There are still a lot of new features being introduced to the core Android APIs, with fragmentation issues being mitigated by a provided support library [0] which essentially backports the newer APIs to older versions of Android (some new features are only in the support library).
Android as it's sold in most consumer devices obviously isn't entirely open, but Google still seem to be attempting to strike a balance between supporting the open-source platform on the other, and building up a suite of closed userland features on the other. You might disagree with their judgement on where the balance is, but I think it's unfair to say it's being developed as a completely closed product.
[0] http://developer.android.com/tools/support-library/index.htm...