I currently have a 3GS and am planning on getting the new iPhone when it's released, and will give my 3GS to a family member when that times comes. I'm excited about the new features for iOS6, but I'm a little wary of the performance. Upgrading from iOS4 to iOS5 was quite nice, but it caused a large number of performance hits when it came to app loading and switching between apps. Even bringing up my Messages would cause delays in which I could count to "10-Mississippi" before finally being able to let me interact with it. I don't expect it to perform the same was at an iPhone 4(s)/(new one), but it does make me grit my teeth a little sometimes :)

Agreed - the iPad 2 is also still being sold, so there's incentive to support that too (over the iPad 1).