I've been burned by Google too many times, but I'm definitely thankful for them continuing to maintain Voice, and even actively improving it over the last few years. I've been using it as my primary phone number since the GrandCentral days, so it'd be a pretty big pain to have the rug pulled out from under me at this point.

It would also be pretty shortsighted from a business perspective, IMO. Voice could still be extended to compete with iMessage and WhatsApp, like they sort of tried to do back when they were going to merge it with Hangouts.