a) There seem to be basically 2 camps, with very few in between. Some love it, some hate it. I happen to fall in the latter category.

 

b) Very hard to tell at this time. WotC's track record for anything to do with the internet is terrible. If they actually deliver on all the stuff they've said, it could be interesting, but the odds are in favor of an epic fail.

c) Older sets had seen continued increase in value until around the 2.0/4e announcement when they took a dive. I'd wager that with a some exceptions that they're not too awful far from where they were when you left. Corim mentioned dhunton's list and I think it's an excellent resource as well.

d) It remains to be seen what will make the cut to 4e. They have taken many monsters that would be considered MM1 shoe-ins (like the Frost Giant for one) and held them back to put in later MMs in the hopes that it'll make them sell better.

e) As Corim said, it really depends on what you want. Older minis will always be useful for rpg, but if it's skirmish you're after, they have instituted set rotation. There is going to be a vintage format in which all the old pieces will be legal once they have been restatted, a process that will likely stretch well into 2010 if not longer, but it remains to be seen if the support will be there. personally, I think with 4 formats (Standard, Limited, Epic and Vintage) that one is bound to get the shaft an I figure it will either be Epic or Vintage.

Some people do. I don't. My D&D future lies in any version of D&D not called 4th Ed. I've also been looking at Pathfinder by Paizo.

I honestly can't say. However, I don't envision a time where online minis gaming replaces table top minis gaming.

Values have gone down since the announcement of 2.0

Dunno.

If you can get the older ones on the cheap, why not grab them?
I'm guessing you won't see 4e equivalents of all of them.