too bad, was my favorite design for the iPhone (aesthetically and tactility-wise).
I agree it's probably time to drop it since you'll have 3 phones and the new iPhone soon on the market. Seems a bit much.
Personally, I don't see the point of having the iPhone 4 and 4s both on the market right now. Really the only major differences were A5 chip, SIRI, World phone chip and better camera...that's it.
So I really don't see why they'd keep the iPhone 4 around. Why not just sell the new iPhone and the 4s? Maybe just keep the 3GS another 9 months and retire it just before WWDC 2013.