Couple of things...
The K-Mount is probably the least-obsolete manual-focus lens mount that there is - in that my Pentax *ist DS will work with every K-mount lens ever made, without modification of the lens or the camera. Show me that with a Canon, Nikon, or Minolta (now Sony) lens mount over the years. The K-Mount has changed, yes, but has preserved backward compatibility. So it is a pretty logical lens mount to support.
Second, although there are indeed plenty of classic K-mount (and M42 mount) SLR cameras out there - most of them are pretty old now. They were very well-made, but they're still old. Many of them never had TTL metering or higher-than 1/1000 shutters. They are in need of service, from refoaming to a total rebuild. On the other hand, lenses can be kept in a drawer for decades; if they don't get fungus, then tend to be just as good as they ever were. So why not build a modern camera to support the old lenses? Makes sense to me - but then I have a Bessa R (rangefinder), a Bessaflex TM (SLR) and some of the classics too. Guess which ones I take out and use? The modern bodies, with the classic lenses.
Third - to understand why the Voigtlander name is being used by Cosina, you really have to have an idea what the CEO, Kobayashi-san, is into. The guy's a camera nut. He loves the older cameras, and he wants to do them homage. When he made his Bessaflex TM SLR that looked like a classic Topcon, he went to the Toyo Optical Company (who used to make the real Topcon) and got their blessing to do it. The guy's for real, give him his props.
http://www.popphoto.com/blogsandcolumns/2307/speaking-frankly-the-contrary-mind-of-hirofumi-kobayashi.html
Kobayashi bought the rights to use the name 'Voigtlander' from Ringfoto in Germany and he basically revived the nearly-dead rangefinder market. He reintroduced M42 screw-mount lenses, made to mount on all those M42 cameras out there, and he's even done Contax and Nikon RF mount cameras and lenses. Basically, he's serving very tiny niche markets, and selling them at incredible price points given the size of the market (usually boutique market items cost MORE, not less). I suspect if it were not for crazy Kobayashi, we'd have none of this Voigtlander stuff, no rangefinder revival, just a bunch of boring AF digital cameras and dying film cameras and nothing interesting except maybe Lomo, for whatever that's worth.
Is Cosina Voigtlander 'the' Voigtlander? No, not by a long shot. But here's a clue - the 'real' Voigtlander is dead and gone, and to revive that company in the form it existed - quality and all - most of us could in no way afford it. You want to pay ten grand for a 'real' Voigtlander camera? I can't afford it, can you?
So what it isn't a 'real' Voigtlander? I don't see it as Cosina stealing the famous name - I see it as a guy who is crazy for classic cameras, supporting a niche boutique market just because he wants to. So for this, we should all spit on him...right?
I can understand people having a problem with someone using a famous name to make shoddy products - I'd be mad too. But Voigtlander - the original Voigtlander - is dead and gone. They're not coming back, ever. Cosina is trying to do them honor, not destroy their name. Everybody who is interested in these cameras knows perfectly well that this is not the 'real' Voigtlander. It is no secret, and no harm is being done. This company is legit, and they show us a lot of love. Real camera enthusiasts making cameras instead of bean counters. What's not to like?