If you do this, please call AP Member Services and make sure that your APs are prioritized correctly in your account. This is something that they can seen on their side and change if needed, but you cannot.
I did this once. I had an activated AP (
DVC Sorcerer's Pass with Photopass & Water Parks). I was planning to let it expire due to a few months gap between trips. But I went ahead and bought a new AP, not a renewal, locking in today's prices but not planning to activate it until multiple months after my previous one expired, but still well within 1 year from purchase.
Then I went on a trip where it should have used my currently activated AP. However, when I went to Typhoon Lagoon, it didn't use my currently activated AP. Instead, it automatically activated my new AP that I wasn't planning to activate for several months. It took a long time to try and sort it out with WDW. At first, I incorrectly assumed that they unactivated my AP. However, they just tacked on a couple of months to my new AP. Then when I took the trip that should have activated it, I realized it didn't give me a year from that date. I probably spent an hour a the Guest Relations desk in Magic Kingdom trying to get that resolved.