I think he's still eligible to win it, but my understanding is that, if you are under the age and games threshold, and have already earned a rising star nomination prior to the season, you can still win the award. No doubt Jones will be in the running, yet why bother nominating him, when he already has got a nomination last year. It's better to nominate another "rising star" and give them a chance at winning the award/ at least boosting their confidence knowing that they are "rising stars."
Jones definately has a chance to win it.
Unless they've changed the rules, you have to be nominated in the same year to win. Duncan Kellaway was nominated in different years, and I think there have been a couple of others.