Amazon requires that you offer all versions of your app for sale on Amazon. So they will be selling your Google Edition as well as your Amazon Edition.
Everything? Does BitBucket support git? I thought it was using Mercurial.
Mercurial is great, but it's not git. It's a hassle to have to learn two ways of doing everything. (Being intimately familiar with git's required these days, especially for Linux and Android programmers. Mercurial's not.)
Is it a video game (use C++) or a web app (use PhoneGap), or a normal app (write everything twice, 'cause users expect platform specific look-and-feel.)
For what it's worth, two additional cross-platform frameworks you might want to look at are:
Corona (Lua-based, already used for hit iOS games.)