I find it somewhat strange that the German motorsports media hasn't picked up on the BMW-to-GT500-rumours. I guess the times, where every little rumour that involved the DTM was reported are over. Maybe Radio Le Mans doesn't have such a good journalistic reputation at all (Not my opinion, just a guess
)...
In any case, I don't see why BMW should build an all-new SuperGT car from the ground up. Yes, there are some differences between a DTM and a GT500 car. But BMW can easily modify the external difference and I'm sure that they can develop a 2.0l R4 turbo in a rather short amount of time. They could just modify their WTCC engine after all (If it works...). As for the drivers: I'd guess that BMW would hire drivers with experience on DTM cars and pair them with Japanese drivers, who know the courses. Candidates would be guys like Andy Priaulx, Dirk Werner, Joey Hand and so on.
Overall, it'd be really nice to see BMW in SuperGT and yes, I hope that Mercedes and Audi follow suit. That way, they could help SuperGT to conquer the Asian market, without having to drag DTM to Asia. But I guess Mercedes doesn't have enough money, while Audi will point to the Audi R8 LMS Cup as a "proof" of their existing engagement in Asia.