The answer the OP is looking for is YES They have thought about this, hence all of the discussions about Meego certification and branding. A key tennet of Qt is ABI forwards compatbility.

As long as the ABI stays stable recompilation is all that is needed (which I need to do whenever I add features). Linux has worked like this for years and runs on everything from mainframes to handhelds, so already a proven model (with well understood issues that cause ABI breaks).

However cockups do happen (like recent hardfp issues with ARM Meego) but in principle as a developer I would feel comfortable to trusting the Qt crew in limiting issues that create ABI breaks.