Amazon's customizations are purportedly deeper and better then Honeycomb. Proof will be in the pudding of course but if you were doing a significant fork you can't just keep restarting over and over to incorporate everything Google is doing too.
In that case it would be a huge gaffe on Amazon's part. Amazon will have to be responsible for the full OS and it will be a nightmare for them to integrate whatever Google is pushing out every 6 months, including security fixes.
But let's put that aside - think about compatibility from user stand point. Google's app store is still the main Android app store and is likely to be so going forward. If Google and its partners start pushing out newer releases that Amazon fails to incorporate in their 2.1 tree - users are going to miss out on apps - when they have a 2011 era dual core hardware that they paid $300 for.
Again if this was $100-$179 it would be OK - $300 is what makes this not attractive.
Keep in mind that it wouldn't be particularly difficult for the Kindle tablet to outsell all the other Android tablets put together. If that proves to be the case, why would they have any difficulty attracting apps?
Amazon's customizations are purportedly deeper and better then Honeycomb. Proof will be in the pudding of course but if you were doing a significant fork you can't just keep restarting over and over to incorporate everything Google is doing too.