PoW coins are slowing going out of fashion it seems.
All the new coins are PoS based and some are doing quite well.
This naturally makes sense, PoW alts can't properly secure itself anymore because of either Scrypt Asics, botnets, or simply not having the hashing power of Bitcoin. I expect many PoW alts to start failing and continue decreasing in market share because of this. Look how litecoin just recently lost number 2 in market cap --
http://coinmarketcap.com/ The exception to this are coins that depend upon the security of bitcoin blockchain like coloredcoins , counter-party, mastercoin, and namecoin.
There's nothing to stop a well funded and determined attacker to attack Bitcoin's PoW network in the same fashion, it's still only cost 10% of Bitcoin marketcap to attack. That's extremely cheap compared to buying 51% stake in a PoS eco-system.