The focus on Bitcoin has kept participation from other cryptocurrencies to a minimum. When the site first launched, the decision made a lot of sense: most of the "alt" currencies were simple forks of Bitcoin. But since then, new currencies have become a testbed for innovation and many solve entirely different problems. We should either focus excursively on Bitcoin and sidechains or revise the FAQ and change the name to include other currencies.
This is not fueled by a motivation to marginalize Bitcoin. The second major cryptocurrency, Namecoin, was started because Satoshi didn't believe in piling every proof-of-work system onto a single blockchain. Academic research is first tested in new currencies, such as Zerocoin, because it is easier to experiment with a new currency.
However, we are now seeing the first wave of currencies with radically different designs, such as Ethereum. BitShares innovated on the very definition of value. Even the Tor developers are working on using a cryptocurrcy to improve network throughput. New currencies are more than just an "alternative" to Bitcoin, they offer new solutions and solve different problems*.
Being "officially" neutral and allowing questions about other currencies isn't enough. Users searching for answers on Google won't know what the official policy is and experts in other cryptos are turned off by the name. Since we can't get any traction here, Namecoin (which is specially cited in the FAQ) is considering switching to Vanilla forums so that we can offer a Q/A system. Even discussions regarding different types of PoW or specific applications (like decentralized markets) are seemingly off-topic for a "Bitcoin" SE site.
The Bitcoin name and URL only makes sense if you are primarily interested in Bitcoin. This is incredibly self-limiting in a future filled with cryptocurrencies that solve different problems. C is still the language of choice for many applications, yet we've seen many successful new languages over the past forty years. If the original StackExchange had restrained itself to a specific technology, it never would have had such an amazing impact on the programming community. If we want this SE site to become a vital resource for the cryptocurrency field, then we need to truly embrace other cryptocurrencies. I think we should update the name and URL (perhaps Cryptocurrency and
cryptocurrency.stackexchange.com) and update the FAQ.
We are still in Beta, but time is running out. We need to either widen our audience to embrace other currencies or narrow it and restrict discussion to Bitcoin and sidechains. Officially allowing questions related to other currencies while discriminating against them prevents future SE sites from building their own communities.
Update addressing posted answers:
Arguments about the popularity of Bitcoin don't make sense in the long run. The situation is a bit different, but it's not far off from claiming that StackExchange should have been called JavaExchange. Even Satoshi thought that piling every PoW system on Bitcoin was a bad idea, and Ethereum, BitShares, and others are proof that Bitcoin isn't going to be the only cryptocurrency that matters.
The argument that other currencies aren't trying hard enough is like claiming that the name "JavaExchange" wouldn't have alienated users of other programming languages. Arguments that we just need to make tweaks are like claiming that JavaExchange wouldn't be dominated by Java questions if they just tweaked a few things, like the FAQ.
This really comes down to usability which (no offense intended) is something that I think most technically minded people have a hard time groking. People don't read the FAQ or the intro! The Bitcoin name effectively makes this a site about Bitcoin.
What do we gain from keeping the Bitcoin.SE name? What would we lose by switching to Cryptocurrency.SE?
Switching to Cryptocurrency.SE would reduce bias in search results, user perception, and the community. Cryptocurrency.SE will still turn up in searches for Bitcoin, but users won't mistake it for a Bitcoin only site.