There's a difference between "need" and "support".IMO SC2 will not need GL3.0
"Support" is like how Crysis supports DX10. It has a DX9 renderer too, but that doesn't stop it from having a DX10 renderer as an alternative.
"Need" is something different. "Need" is, "you can't run this without R300/NV30-class hardware." That's the baseline minimum these days.