"Would" with the perfective and progressive aspects

Consider:

A.1. The guests will have arrived last night. I could hear voices in the next room before I went to bed.

A.2. The guests would have arrived last night. I could hear voices in the next room before I went to bed.
&
B.1. The lights are on. John will still be reading his paper.

B.2. The lights are on. John would still be reading his paper.

Can both A.1. and A.2. be glossed as: It is almost certain that the guests turned up last night?

Can both B.1. and B.2. be glossed as: It is almost certain that John is still reading his paper?

Any nuances between A.1. and A.2., B.1. and B.2. respectively?

• The only one of these construction that I've heard and would use is B1. Note that I am a speaker of American English and some of these (particularly A1) sound like they might be common in British English. I really wouldn't even say B1 ever. Instead I would say "The lights are on. John must still be reading his paper." Or "The lights are on. John is still reading his paper." Would and will feel more like they belong in conditional statements, and there are no conditions in these sentences. Sep 15, 2015 at 13:19
• @ToddWilcox I totally agree, but the question I quoted in the tetsujin's comments says "would have done" can be used to make an inference. For example, A: A message was left on your desk. B: That would have been John. How do you account for this? Sep 15, 2015 at 14:48
• A2 doesn't seem like an inference, instead it seems like a conclusion. "I could hear voices in the next room before I went to bed last night, therefore I conclude that the guests arrived." Contrast with, "I have no information about what happened, but normally the guests would have arrived last night." Similar with B2 - the lights being on is too much information. Strangely, just knowing the time alone makes more sense for "will" or "would". As in: "It's six o'clock, John will/would still be reading his paper." We don't have any evidence about what John is doing except what he normally does. Sep 15, 2015 at 14:59
• I see now I'm agreeing with Testujin: There is too much evidence/information for "will" or "would" to normally be used in these cases. Knowing or concluding based on other facts is different from inferring or supposing. Sep 15, 2015 at 15:03

A1 'will have arrived' would suggest you have strong certainty that they should have arrived, but no absolute proof they did. Your second sentence appears to be that proof.
That would make A1 into

"The guests arrived last night. I could hear [their] voices in the next room before I went to bed."