li10up, I'm been worried about the same thing but feel like I've come up with a decent plan that will keep me motivated and in decent condition. While I'm going to miss the bike, I think it will be good to take a break to avoid burnout. It seems to me, too, that off-season is a good time to work on building a better foundation for cycling and to improve overall conditioning.
(I would note as an aside that I started cycling this year and that, like you, my first ride was 6 miles and my longest ride was last weekend at 65!).

I've been practicing yoga about twice a week since May. I intend to keep that up. One, I love it and, two, it helps with core strength, balance and flexibility. When I'm cycling a lot, I find that it smooths out a lot of the kinks.

I've recently joined the Y and have already starting taking spinning classes 2-3 times a week. I usually hate working out on gym equipment, e.g., treadmills, stairclimbers and the like, but I love spinning. I can already notice a difference on my bike with power and consistency. From an aerobic/lactic threshold standpoint, it will definitely benefit my cycling and overall conditioning.

I also intend to develop a weight training program with a trainer. I recently purchased a book called Bike for Life that suggested strength training, not only for the muscles most used in cycling, but also for the ones that get underused and imbalanced. Seems like a good idea.

I need to do something more, however, that's "weight bearing" to counteract the fact that cycling isn't. I don't want to neglect my bones! I'll probably end up speed walking/hiking. The Y also offers fencing--which sounds fun. Again, I think working on my balance and reflexes couldn't hurt.

Beyond that, there's always swimming, running, kickboxing, pilates, etc. I plan to mix it up and keep it fun.