Whilst Litecoin has the best chance of doing this I personally do not feel anything will replace Bitcoin.

I am actually quite convinced that something will replace bitcoin - if not this year, then the next one. And my reason is a very simple one:
BTC was born in and lives in a high tech environment, but it has given up on leading in innovation. It's large network won't save it from that.

I have no idea what will replace BTC, but considering how much division there is within it's community, I highly doubt it will change pace.

My thoughts on who would be a likely candidate: A feeless or allmost feeless blockchain. If there is a way to not pay a middleman, with usability and convenience being equal, why would a majority of people, who have no preference to a community/technology/or anything take the option with fees?