2 iPhones one SIMM card

I currently own an iPhone 3G and will be getting the new iPhone when it is released. As personal choice I do not jail brake or hack any device under warranty. So my 3G is jail broken and i use it as a wifi hotspot to connect my iPad when not near a wifi connection.

My question is this, when I get the new iPhone can I simply keep my old phone handy and when i need a hot spot just swap SIMM cards while i need to?

Truthfully the only place I really need it is in a couple of classrooms at school that don't have wifi access.

Since you have stated that the device in question is Jailbroken, it's pretty much off limits here. Lots of places on the web to get info on this, go find them.

'nuff said.