Awhile ago we were in the same situation of not knowing what to do. We decided not to renew and get the extra months from the date we purchased our new passes. In fact, I asked the same question on the DIS. Someone gave this advice: If you don't plan on a WDW trip for at least 3 months from your renewal date, it is usually a better deal NOT to renew, but to simply buy a new AP when you finally do get back to WDW.
Besides, you never know. Something could come up and maybe you won't take the January trip.