Let's assume, that in ten to twenty years, blockchain is a word everybody knows like everybody knows the word internet.
Ok, if 'blockchain' becomes that ubiquitous then, like the internet, we'll have more and more alts functioning regionally like ISP's and filling their own niches.
So in my estimation: MOON OR BUST!!
Hmm, I doubt that. Unless, we will see something that is not that common at the moment but might be in the future: Throwaway blockchains, i.e. blockchains that are used for a short period of time for a very narrow purpose and are discarded or archived afterwards.
I'd expect them to be associated to a "motherblockchain", though, so I wouldn't really count them. I wouldn't count things like Iconomi, Blocksafe, SingularDTV and other tokens issued on an already existing blockchain either, for that matter. I expect to see tons of those, but I think there are going to be only a few "motherchains" to build upon.