I don't know, I used to resist people's comments about Google shutting everything down, but I find myself on that side of the fence more often these days. With that said, I would be surprised if Google shut Fitbit down. Wearables seem to be big business when done right, and Fitbit is the best thing outside of Apple watches (not counting Garmin, they are in an upper tier imo). I think it's in Google's best interest to properly integrate Fitbit into their company and help it grow.

Usually the hardware companies they kill off eventually, Nest being the outlier.

I'm not saying that they'll 100% kill off Fitbit, but it's very likely. Google already does hardware and software that does a lot of the same stuff, no point in having 2 brands.