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

I read this offline during coffee break
I totally have the same opinion
it may change in the future
but for now BTC is the most accepted crypto currency in the physical market and when those shops in Japan officially start accepting it - it'll be like a hamehamewave :)
but i am not a fortune teller so I don't hold the truth :)
we shall see