CPU-based altcoins might still work though.
Bitcoin certainly wont work anymore with CPU-based mining. In the mining board someone wrote:
You would have exactly a 0.000000000082930% chance of hitting a block over a 1 year period running at 99.999% efficiency 24/7
There is a list of CPU mining coins here
http://cpucoinlist.com/That list isn't bad but
it hasn't been updated since mid-2014 so some of the information isn't quite up-to-date:
Wild Keccak has a GPU miner; the advantage is known. There are rumors of a particularly performing GPU miner.
X11 is well known to have private elite kernels which can be easily 2-4x more efficient than public.
Groestl2... there was some turmoil with GRS some months ago... I'm not sure this is worth considering.
JHA remains in the realm of "CPU" coins because nobody taken care of resolving the borderline trivial "complications" they introduced.
Cryptonight is known to have private implementations.
Let's say the others are fine.