Oh I dunno, I've yet to notice anybody complain about them using pre-existing TOS characters in cameos.
But there has
been a call for "Give us something new", both before and after the return of Khan. Not to mention all those issues that wee remakes of TOS episodes.
The problem is that any guest TOS character IDW does use from the Prime Universe will probably end up clashing with future movies if they choose to use that character, or it suggests that Orci has no plans
to use that character (ie. Gary Mitchell, Robert April, T'Pring).