The technology is solid and has the potential to change the way we do MANY things... and then there's the fact that we're still on the bleeding edge of any kind of mass adoption, so there's a LOT of money that could potentially flow into the market.
Now, it BTC always going to stay the "big dog?" Probably not. For all I know, 20 years from now we'll be looking at a set of alt coins that don't even exist today.