My guess: After selling a lot of G28 and the profit of groestl drops, they will release groestl for X10.
Imagine they would have done this now or 1-2 weeks ago. Then the X10 would have diminished the groestl profit and the G28 would not have this high profit rating on several sites. This is of course only for the less informed buyer a thing. But I think a lot of buyers just see the numbers and dont check network hashrates and stuff. If you buy, calculate with the Qubit/Quark/Skein/X11gost profits.