I don't even have a 360, but I can tell you pretty much most of the answers to this:
1) 0 for myself obviously, though I think pretty much all that I know who have a 360 have gotten it at least once
2) As long as Microsoft replaces it for free, of course they won't get rid of the system. Once you've got bout 3 or more games for a system, getting rid of it just isn't practical. The only reason that there would be to get rid of the system is if you would have to buy a new console, at which point THAT would become even more impractical.
3) That will still likely depend more on what the next console is capable of. After how much trouble the RRoD has caused, no company would be stupid enough to risk that again. Having a long series of RRoD that cause personal events to be disrupted (like if buddies come over to play or missing out on an online deal or something) might cause people to look towards competitors first. If they held out from getting the PS3 or the Wii and the PS4 or Wii2 are backwards compatible, that might be further incentive for them to go towards those consoles first.
Personally, the RRoD is about 50% of the reason I wouldn't consider 360 as a second console, the other 50% is that any of the HD games that I'm mildly interested in are all multiplatform combined with MGS4 and LBP being PS3 exclusive.