> Also is it a concern that the half frame sensor might one day be left behind when full frame gets cheaper to make? If so then what future for DC lenses?
Personally, I don't think it will happen anytime soon. Generally, electronics get cheaper and cheaper because it's possible to pack more and more stuff into a single, tiny chip. Small chips are cheap, but big ones are not. Here we'd like to increase the size quite a bit. Not 50 %, not even 100 %, but up to 150 %! A full frame sensor is indeed 2.5 times as big as the 1.6x crop sensor used in Canon 20D and more than twice as big as the sensor used in the 7D.
The production costs would rocket up because a bigger sensor means not only less sensors per wafer, but also a higher percentage of faulty ones because the probability of manufacturing defects is proportional to the surface area of the chip.
> Do some of the independents make the branded lenses for the camera manufacturers?
It may have been happening all the time...
> for example the Tamron lens appears to have a similar design to Minolta?
Indeed. Looks like all new wide-angle zooms KM has introduced have actually been made by Tamron. Of cource, there are some cosmetic changes and some even claim the lens coatings are different.
This kind of outresoursing makes sense, because KM can now focus on the production of high end (SMM) lenses and new DSLR bodies. That should help them with their poor street credibility. KM gets constant bashing for not having a pro body or some exotic lenses. "There's no upgrade path" they'll say to anyone considering the 5D. Of cource, it does not matter at all if such lenses or bodies cost an arm and leg and the first born... That's not the issue. The issue is if such lenses and bodies exist, just in case.