Earlier quoted context omitted.
They have a very clear history of buying companies, carving out what they need from it and reselling it (Boston Dynamics, Motorola, HTC, etc). Chances are that Fitbit won't be around 2-3 years from now, hence no real reason to invest in a product from them now.
Like everyone who has an account on HN, I'm aware that there are companies acquired by Google that no longer exist. But some -- Android, youtube, Nest, etc. -- still exist. What makes you think Fitbit will fall in the former category? Random probability?
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.