I didn't see a specific thread talking about the subject, so I hope that this hasn't already been discussed to death.
If the Klingons appear in the new film with ridges, how will that be explained? Klingons in the mid-23rd century should not have cranial ridges! Wouldn't depicting Klingons with a ridged forehead in the new film be a slap in the face to Trek canon and history?
Abrams could argue that most people who see the film won't care or have even heard of the augment virus, but some fans will care and for the integrity of the franchise, the Klingons should not have cranial ridges.
Did you miss the TOS movie that had Klingons with Ridges in them? Those movies are Canon and TOS and had Klingons with Ridges. <Suddenly finding myself craving Ruffles Potato Chips>
TMP takes place in 2273, at least six years after the events of "Errand of Mercy" (2267) and other TOS episodes with Klingons.
I guess the best explanation is is that both kinds of Klingons existed in the late 23rd century.