Assuming Yorks v. Sussex ends in a draw, a Hants draw against Yorks ensures safety. But Yorks will be hungry for a win to ensure their safety. So if Hants lose to Yorks and Sussex beat Notts (will they possibly roll over as revenge for last year??), then it's squeaky bum time.
If Sussex do win their last match and Hants lose, they could both finish joint second bottom with the same number of points, wins and losses, and their head-to-head record point-wise is identical: if so, anyone know who wins the tie-breaker?