It didn't translate 100%, but even a pro player in Starcraft1 unsuccessfully transitioning to Starcraft2 still played at an insanely high level relative to the general population. It was the difference from maybe being a top 50 player before to a top 500 player after. I would say that this is evidence of a very high carryover.

WC3 => Sc2 is a much greater leap than sc1 -> sc2 but still there was decent carryover. Grubby was still a GM or high masters player, even if he was no longer elite.