IMO, it would be better to just switch to a new POS coin. There would be too many problems with miners and early adopters interest in order to make that kind of change in bitcoin. They probably won't allow the change, until it would be late.
Bitcoin will have 6 % inflation in 2016, 5% inflation in 2017, 3% inflation in 2019, and 0.5% inflation in 2026
You overlook an obvious thing:
Transaction fee will increase to compensate subsidy decline. One way or another Bitcoin holders will be paying tithing for burned electricity. The only alternarive is to stop sending transactions but in this case the transaction fees will just go higher.Indeed. And if fees don't go higher there won't be enough security in order to protect bitcoin.
The only thing I know for sure is bitcoin mining is doomed for the longterm. It's way too inefficient, old fashioned and tends to centralization. It was ok as a first step or an experiment, but not for a real economy or to go really far.