What do the other manufacturers have to offer to the ecosystem? A few things, like the Transformer Prime, have been genuinely innovative devices, but it seems like they mostly just dump their own UIs on top of old versions of Android and act like that differentiates their products.
However, I still think that Google could have taken control, and released it's own hardware (although the Nexus 7 is an Asus tablet first shown at CES ... mostly) with some profit($249 as the starting price) built into the equation, and still sold boatloads.
They are raising the minimum quality/price ratio, and that's a good thing.
Hardware production prices will eventually fall and there could be a profit margin there for manufacturers if they stick to the $200 mark and don't lower it.
Somehow brings to mind the PC market before the white boxes took off.
I don't think any company that is not subsidized by Google (i.e. Asus in this case), is going to get out of the tablet business.
So yes, the Nexus is a fantastic device at a fantastic price, but my hopes of a vibrant ecosystem for Android tablet -though previously low- seems further diminished.