Apple iPhone 3G

I already am on a family att line, im pretty sure we have everything basic(eg. basic texting, basic minutes)....how much will the plan be for me?(yes, i am eligible for an upgrade)....and i hear theyres 3 different plans, how much for the basic, and most features?

also, anyone know when the next version will come out?....i was kind of hoping to have more memory than 16 gb so i could actually substitute this with my ipod.

Thanks!
-Tman