Plus, typically, even after an alliance change, already-ticketed award tickets are honored as issued. So, I think your only possible worry is if JAL stops operating altogether (or, if as some propose, they stop operating internationally and leave that to ANA). I just wouldn't worry about it too much - airlines have been known to go out of business, change schedules, drop certain routes, and so on without notice, and you'd worry yourself silly if you tried to plan for all contingencies. If you really wanted to be paranoid, consider making sure that your hotel isn't non-refundable and canceleable up to a few days before arrival.