If your looking to be tided over for only a year. Yes one of these cards will do it as long as the rest of your machine is fast enough not to bottleneck the card. Remember your PSU will probably need an upgrade with a single card but most likely for sure with dual cards. More system specs are needed to conclude.
Depends on what games your playing as well as the resolution and settings you want to play them at. If you currently have one GTX285, an SLI capable board, and a PSU to handle it then I say go ahead and buy another one so that you can enjoy playing games on high, if not max settings, for some time. If you're considering buying two GTX 285s, don't. You're better off with a Radeon 5870.
nVidia's new cards should hit the streets in 5-6 weeks.....even if ya don't buy one, there release will push prices on other cards down. As for which one.....
thats like asking why do you go to this store when there another store that has the same items for cheaper price.
It's personal preference.
You honestly shouldn't be shocked that people are still buying nvidia cards. There many people that dont keep up with todays tech news (like us) but are system builders. They probably remember that Nvidia is (to us "was") the performance champ and will stick to that.