I have wireless on my desktop, no problem here gaming with it. I don't see how it could be - the online game speed is limited by the broadband connection, my wireless signal is strong and doesn't lose packets. I use my console on a wireless connection too.
As for a console idea - every 3-4 years is rubbish. The 360 is now just short of 5 years old, and the newest model is still essentially the same hardware - it's still got a good few years of life left in it.
OTOH, if I get 5 years out of my PC (which cost just under $4k at the start of the year) and have to buy something completely new by then - I'll be fine with it because this type of hardware changes a LOT faster than consoles.