If I switch from a prepaid phone to iPhone, could I keep the number?

I need to get a new phone, but I really want to get the new iPhone that is probably coming out later this year, so I'm planning on getting a cheap prepaid phone then switching when it comes out.
Would I be able to keep the same number when I switch?

Yeah, ask your network provider to convert numbers.

I think you should but it also depends on the company. Straight Talk & Virgin Mobil would do that though.

No, i phones have member ships on them