I don't think anyone would complain. Though according to Wikipedia:

"He currently is suffering from tinnitus, which Steve himself predicts that he will be deaf by 2013."

That's not good.

They could remaster the old sound clips, especially because they're not having any new characters or "alities"

That would be really lazy. Rehiring him would be better.

Plus there's no sound clip for "Goro". B)

Still, lazy or not, it would be their only option if they wanted to use him but couldn't