It won't turn into a price war. Why else do you think they lock you into contracts? It was never to benefit you.
Semi agreed the only price wars will be in the prepaid sector if there are to be any price wars. It could turn into a "non-calling features & extras wars" where the price stays the same but features and extras ( IE: more or faster data, free Apps and offers) will now be added in for no cost. Similarly it has happened before with Long distance, caller ID, 3 way, voice mail, etc... Remember when we had to pay extra for those features?