Hi Elbridge & welcome. Congratulations on your weight loss!
Surgery is definitely a life-changing move. It's a great tool if you're certain you're ready to commit to a new lifestyle but if you have serious doubts, you should probably talk to your surgeon about pushing out your date a few months. That way you can continue with your current program and revisit the decision in say Feb or March. I'm sure people do that kind of thing frequently. Of course, you could always cancel but if you wind up deciding that you want the surgery after all, you may be required to start the process all over.
With the holidays and winter ahead, it's probably the hardest time to loose weight so I think it's a perfect time to put yourself to the test. If you continue to loose and are happy with your progress, that's wonderful. If you loose steam or have trouble sticking with your program, you still have the decision about surgery ahead.
On a personal note, I myself had cancelled surgery twice. Both times, I did so well on the pre-op diet that I lost massive amounts of weight. Unfortunately, both times I ended up loosing steam right before hitting goal weight and proceeded to regain more than I'd lost, quickly. My decision to follow through this time wasn't to loose the weight (can do that on my own), it was to have a tool to keep it off. Just something to chew on.