In the end what matters is whether overall this whole thing is worth it for Amazon itself or not and they are very good at analytics. AGS is not some end all be all Amazon's all hands on deck priority. It has budget and if it constantly goes overbudget and underdelivering they will just cut the whole thing.
And quite frankly AWS does not need to sell itself.
The point is - people keep saying "but Amazon", but the reality is that AGS needs to deliver and perform to continue getting the $$ and so it happens that AGS could not really afford baking the game another year despite "but Amazon". It is extremely likely if they'd delay another year - heads would roll or worse, whole thing would be "reimagined", because in the end AGS answers to decision makers outside AGS who keep the lights up.