What could happen is another consensus layer that gave the right features and supplemented PoW was added to Bitcoin or people just used it with the Bitcoin protocol. This may happen in the future.

What if you had a TaPoS layer that had 1-10 second confirmations which worked with the miners where peoples wallets reflected both the ~10 min confirmation and the 1-10 second ones for added security and to allow for on the sidechain transactions to occur while not giving up on PoW security.

So a TaPoS blockchain could indeed supplement Bitcoin and at the same time would not change any of the core principles like disinflation 21 million , PoW, ect..

The fact that this can be done does not bode well for Nxt or Bitshares and should have them concerned.