I'd prefer that these alternate block chains use different forums, though I would consider creating a section if a really popular alternate block chain appeared. Ixcoin and Namecoin are not there yet, and I'm convinced that at least Ixcoin will disappear soon.
If an alternative were to come up to become popular, why not just make a thread and sticky it.
Having a section just for a fork would almost be like an insult (for how I see it, personally) to the Bitcoin economy.