I just posted an article on my blog where I quoted the founder of NoFiatCoin as saying he thinks mining is going to go the way of the dodo: http://crypt.la/2014/01/31/eventually-mining-is-going-to-be-dead-and-ripple-will-rule-says-nofiatcoin-xnf-founder/

I agree for the most part, though I could see bitcoin being the exception to the rule (and perhaps litecoin, too). That said, I believe the vast majority of the 500 other altcoins are toast. There's just no way people are going to devote serious computing power to hundreds of different altcoins for years to come. Even using all that power for bitcoin is disconcerting... I wonder if Satoshi would do it the same way if he got to start over again from scratch?