All Wii's have WiFi, yes. As for what firmware, I think you just go to the settings, and it should be at the top left. 3.4 was the last firmware before 4.0, and like I said, the Twilight Hack won't work in 4.0, they're working on another exploit at the moment though.
As far as the firmware goes, newer games will actually install the firmware updates. I think it was metroid prime, but first thing that happened when i tried to play it was that it updated my wii. As far as price drops, i do believe that Nintendo said they would Not be dropping prices anytime soon.