Acer chairman JT Wang reportedly claimed recently that Apple's share of the tablet market will eventually stabilize at 20-30%, ... and noted that according to past experience, a closed platform will eventually lose to an open one.
While I can see this happening, I don't totally agree, that a closed platform will necessarily 'lose' just because it's closed.
I think it's more likely that the platform with the more successful "paid" application space (or app store) AND competive priced hardware will win.
You need a robust paid ecosystem (more consumers) to attract developers to make apps. You need good apps and competitive priced hardware (as well as convenience) to get more consumers.
Hardware and platform functionality will leap frog each other and commoditize over time, since it's easier to copy ... generally features that iPhone has today, Android will get tomorrow and vice versa.
Apple's challenge is to develop it's paid ecosystem as quickly as it can, AND
keep prices down to widen it's market (even if it means less hardware functionality in the short term) ... And obviously, cutting prices isn't so nice in the eyes of shareholders.
edit: for Google, I don't think, just being open will cut it .. they have to find a convenient way that the consumer will adopt to get good paid apps.
P.