It is annoying when that happens. That said, you can probably make a pretty good guess as to which docks will work between generations (at least until the connector changes) and those that won't. Anything form fitting, having some sort of recess or whatever will likely be problematic where designs such as the current Apple dock or the Twelve Sough Hi-Rise are pretty likely to stand the test of time since all they essentially expose is a dock connector (and an adjustable back rest in the case of the Hi-Rise). It'd probably take Apple recessing the connector for those to cease working, which seems unlikely.Oh Yeah? Guess just my perspective then. My first 30 pin device was an iPhone (the original Edge). Its dock didn't fit my later 3GS (due to the shape of the phone) so I bought another dock. And then I had a 4S, which was a block shape and again didn't fit;
My advice would be to deal with the fact that one day the dock will become redundant, but at the same time be mindful of the form factor if you want to last several phone releases. You probably will find a device that minimises issues for you during phone upgrades.