Unlikely, bitcoin has too many millions invested in it. Both from direct investments as from various forms of infrastructure

People switched from MySpace and many other social networks to facebook simply because nothing was at stake. It did not cost them many to delete their myspace account and open a facebook account.

 But when they need to transfer wealth from bitcoin to another form of even more risky currency. Or even across multiple Altcoins. It's something else entirely.  Not to mention the much more conservative merchants and investors. We are just starting to get bitcoin accepted by merchants and investors. An altcoin will be years behind on bitcoin and any altcoin has to offer serious benefits to all parties involved (merchants, investors, savers, spenders, etc.) for it to gain even the tiniest amount of traction against bitcoin.

It's just not very likely to happen. Ever.

The first thing a merchant will say when you approach him about pump-and-dump coin #20374 is: "we allready accept bitcoin. Why would we want to accept scamcoin #20374?"

And there you are, trying to explain why your coin is better. But it really isn't because they're all the same, a ripoff premined Ponzi to try and make people who think they missed the boat on bitcoin believe they can make more money on scamcoins. The only ones making money are the creators and early-in early-out guys.

Even if one of the Altcoins comes up with something truly innovative it would be 100000 times easier for bitcoin to just update the protocol than it is for the altcoin to gain even 10 000 users