My wife is currently still on the Unlimited Data plan from AT&T, as she got hers in April 2010 before the new data plans went into effect, so it will last till her contract ends in 2012.
If AT&T hasn't gone back to offering an unlimited plan, guess where we will be going to upgrade her 3GS to a 4?
(That is, if they still offer the unlimited in 2012 of course). -- "I reject your reality and substitute my own!"
You get to keep that plan I had an iphone 3G and just upgraded to an iPhone 4 and i got to keep my unlimited. It's a case of if you change away from that plan you lose it and cant get it back but if you stay with it you get to keep it.
My wife is currently still on the Unlimited Data plan from AT&T, as she got hers in April 2010 before the new data plans went into effect, so it will last till her contract ends in 2012.
If you are on unlimited now, you can upgrade to iphone 4 and retain the unlimited plan. I did this for my wife on her 3G to 4G phone back in August.