His reforms, contrary to popular believe did go through. He died but the Senate silently implemented his agrarian reforms (or at least a watered down version of it, not sure) afterwards. Their problem was someone getting all the credit for it, not that they needed to do something.
That said, a surviving Tiberius Gracchus doesn't likely change much. He wasn't anywhere near as radical as his younger brother and wasn't trying to get as far sweeping reform as Gaius. A better POD is having Gaius live. This also helps because Gaius has been compared as one of the best Roman orators in history, just behind Cicero-which means he can work a crowd better than the best of them and has a better chance of succeeding.