I just taught a class on this and I've gotta admit, I'm a bit confused about it myself! lol

What I told my students is this....
Just like the past continuous tense, its usually used to give background for another action.
Its also used to talk about something planned that will be happening (for a duration of time) in the future. However, the sentences you gave for examples had none of those qualities... To me, they just sound a bit more "business-y".

Does anyone else see a difference between her example sentences and the alternatives she wrote below?

I think the difference is in terms of promise compared to planning.

When will your boss retire? (The boss has announced the date that he will retire).
When will your boss be retiring? (The boss has made a plan to retire, but maybe it will change).

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Sorry Sand, I take my comment back about it being more "business-y". I thought about it and I've used this tense before with friends, as well. Besides the uses I pointed out in my previous comment, its often used to talk about definite future plans. To me, the following 2 sentences are identical:

I'll be going home for Christmas to see my family.
I'm going home for Christmas to see my family.

This sentence is a little less definite, though:

I'll go home for Christmas to see my family.

Hope that helps.

vernongstamm, what's with the resume posting? You should do that elsewhere, dude.

All of your sentences, to me, mean the same thing. I don't think there is a difference in nuance, although "Do you know when your boss will be retiring?" sounds a little more formal and less direct than "Do you know when your boss will retire?" Try taking a look at this sentence:

"By this time tomorrow night, I will be sleeping in my own bed."

This implies that at this time tomorrow night you will already be asleep. If you just said, "By this time tomorrow night, I will sleep in my own bed," that almost implies you won't be in a constant state of sleeping but instead you will go to bed at this time. However, if someone said this to me I would know what they were saying. For me, the first sentence sounds more natural. A lot of times you don't need to use the future progressive tense.

That's a pretty good question. I think all those ways of saying it are basically the same, you can use whichever form feels most natural to you.

Zhivago is correct about the retiring though. "Do you know when your boss is retiring?" It slightly implies that the retirement is something that has been announced. However that's not necessarily so, and you won't lose points for using the "wrong" form. =)

The future progressive form also adds a very slight passive tone to a sentence. For example if you go to a restaurant you might be asked:
"What do you want to order today?"
But a way to sound a little more polite is to add a passive tone:
"What will you be having today?"

I really don't know why this sounds more polite, and it is only SLIGHTLY more polite, but I use this form in many of my business emails. I think it makes you sound a little more educated as well. I think the effect is similar to "passive voice" if you are familiar with that.

Along with what Phizuol said, "What will you be having today?" is more polite than "What do you want to order today?" because it is less direct and more passive. You are not directly addressing what they want but instead what they will have. It almost assumes the action will happen and you want to say something about it. Like Phizuol, though, I have a hard time explaining why it is more polite. It just is ^_^

I also agree that it makes you sound more formal. A lot of times it is used by waiters/waitresses, stewardesses, hotel clerks, etc. Basically, any type of employee who is serving you.

Using "will be -ing" emphasizes the difficulty of knowing the exact time.

It's hard to determine the exact time of someone's arrival, the time someone else will retire in the future, and you used "soon" in the other example to show that the exact time is uncertain.

"What time is your friend arriving tomorrow?" is ok. But "What time will your friend be arriving tomorrow?" highlights the uncertainty and the difficulty of giving an exact time.

All of your examples are of the same format, so I'll only discuss the retiring one.

All of the retiring sentences are basically the same. There is hardly a difference in the nuances of the sentences, but here are some observations:

"Do you know when your boss will be retiring?" is slightly softer and less direct than "Do you know when your boss is retiring?".

"Do you know when your boss will be retiring?" is referencing the *process* of retiring, whereas "Do you know when your boss is retiring?" and "Do you know when your boss will retire?" are both referencing the *action* of retiring. The difference is very subtle.

Example:
"Do you know when you will be exercising?" <-- This seems to provide the idea of the *process* of exercising. I can imagine somebody riding on an exercise bike, or running on a treadmill.

vs.

"Do you know when you will exercise?" <-- This, to me, gives an image of the starting point of the exercise. It's not the whole process of exercising, but it's a single point in time.

Conclusion: Using "will be" in these questions seems to give me the image of the *process* of doing the action. Using "is" and "will" by themselves give me the image of the moment of the action itself. Finally, in both cases, "is" seems to be more direct, and perhaps slightly stronger than "will". Again, though, this feeling is so subtle, that I'm not sure that it matters for any of these sentences.

In a lot of cases (like the ones you brought up) these two cases don't have any distinction! You can use them interchangably, but we like to use "will do" "going to do" a lot because it has filler words. I am sure this is a huge frustration since Japanese doesn't have that many filler words.

"Do you know when your boss will be retiring" can also be
"Do you know when your boss will retire" or
"Do you know when your boss is retiring" or
"Do you know when your boss is planning to retire" or
"Do you know when your boss is planning on retiring"

Each have the same meaning, but are just multiple ways to express a similar idea. The first three are similar to each other, and the last 2 are different since they have "planning" in them.

I wanted to say, don't worry too much about the differences if you just want to understand the speech, but I would agree that it is due to an "uncertainty" of the future that we say "will be ----ing"

I agree with Broan. English is full of fillers; like a hotdog.

I think the difference is VERY small and all of your sentences sound perfectly fine to me.

All the sentences sound correct to me, and I don't think I even know the difference. I guess it will come natural depending on the situation. Pick the polite "sounding" ones for meetings and such, and the casual ones otherwise. I don't think I mastered this concept when it was being taught to me. :)) so thanks for those helpful comments! :)