That's a nice suggestion. Applied consistently each coin would have its own independent forum, the Alternate cryptocurrencies section here would be shut down, traffic to this site would plummet and revenue to the operator would plummet along with it. I don't think that lead balloon is going to fly very far.
This implies that every coin has the same community behind it, which obviously isn't true.
Next to no Bitcoin/Litecoin fork has the community to sustain a full fledged forum of their own for a prolonged period of time. Therefore, the best solution for them would be a thread or two in the Alternate Currencies section. If a coin is becoming so demanding that it would require it's own board (on a forum which is essentially unrelated besides it being a crypto-currency), would it not make more sense for that coin's community to transfer to it's own forum, rather than stay on an otherwise unrelated existing forum?
As for this,
traffic to this site would plummet and revenue to the operator would plummet along with it
BitcoinTalk has survived previous to these alt-coins being created and used, I'm sure it can survive should said alt-coins move away.