Here's the problem as I see it:

How many iphone users do you know that are active in an iphone community? Most of the ones I know just use their iphone, they don't get in online forums and discuss, test, develop, etc. Even if the maemo phone gets a large market share (which I doubt, there is a lot of competition in that market), many of the users will be just that: users. People that are unlikely to join the community. I don't think we'll see a large influx of new community members, sure there will be some, but not a lot.

I also think the smaller screen lends itself to a different class of applications. Many of the applications I use would have a very different user experience on a smaller screen. Some of them may not even have been ported/developed or be too cumbersome to be interesting. Lack of a stylus on the smaller screen will play a large role in the type of programs developed.

On the whole, a larger market share may not have as beneficial impact as some believe.