Better to switch it up now, when you still have time to plan, rather than in the middle of November. There's still 20 days to get a new novel planned and ready.

It'd be hard to be successful at NaNo if your current project doesn't inspire you to write. 50K words in 30 days is a lot and if the inspiration isn't flowing, you're going to have a hard time. Meanwhile, if the story is begging to be written, you'll be able to crank those words out a lot faster.