Given Google's terrible track record of shutting down products and services that don't meet their expectations:
https://killedbygoogle.com/
I'd be very, very worried for Reddit's future if they bought it. It's already a service that isn't making the type of money the VCs hoped it would, and which is resorting to desperate measures before its IPO. Google would probably swing the axe down on it in the first 5 years if they acquired.
Outside of that, Google is no stranger to making their services worse too, as everything from Google Search to Gmail and YouTube has shown in the last few years or so. So they're not that much less likely to run it into the ground if they do keep it open either.