That's one advantage to Android. You can change manufacturers for your phone and retain your investment in the eco-system without much issue. Moving from the hot Samsung, HTC, Motorola or Sony model to the new hot model of the week does not make you lose all your apps. Not so for iOS.
I'll be replacing my iPhone 3GS with another iPhone just for this reason. I'd probably have moved on to Android or to another vendor (SAMOLED+ screen is quite tempting, those things are awesome!) if it weren't for this issue.
So in a sense, this high loyalty is probably a result (for some, not everybody of course!) of vendor lock-in.
Lets hope my projections are right then, and applications - hopefully sooner, rather than later - become (somewhat of a) industry asset. With some luck, we'll see a third option materialize soon. This would definitely do wonders for making this particular future less distant :- )