If you've already emailed them, and they're not in stock, I think the best bet in these situations is to assume they're not going to ever be there; at least not anytime soon. I've been scouring eBay, and the prices are pretty ridiculous; not to mention, they're all in Australia. If you can buy more than one, I bet they'll combine shipping. You should ask the sellers and see if you can get a shipping discount to make the prices more-reasonable per-bulb.
I'm betting LiFi Labs produced a limited number of Color 650s, and the bulbs didn't sell well for the engineering cost. Considering the size, they probably can't use the same hardware as the larger A19 and B30 bulbs nor would they fit nicely in your light sockets otherwise. Not to mention, the more LIFX hardware changes per generation, the more work for programmers in updating firmware. QAing these bulbs has to be a nightmare.
It's very possible LiFi Labs is working on a new GU10 light, but if that was the case, they'd say something since there are no Color 650 sales to cannibalize by announcing a new product in that socket.
Philips Hue has a light in that size, but they're fat bulbs. There are some folks that have systems to connect Hue and LIFX together, but man, that's such a hassle, and you lose out on the LIFX app's color precision :/.