Why do you think it's important to have both?  I'm pretty sure we're dealing with a natural monopoly here.  There don't seem to be any significant benefits to having two viable blockchain-based currencies, while there a several disadvantages.

Even if another blockchain does overtake Bitcoin, SolidCoin won't be the one to do it.  To be successful, the challenger would need to make significant protocol-level improvements, and even that might not be enough.  CoinHunter hasn't done this.  Protocol-wise, all he's done is changed a few constants; nothing more complex than what the creator of Ixcoin did.