I personally also think it's currently among the best renderers out there - it's my personal favourite for years.

It's hard to know what will happen, but Altair at least is not Apple, Autodesk or Microsoft who are known to butcher perfectly fine software for parts.
They use Thea as renderer in their Solid Thinking CAD software, so it's unlikely it will die anytime soon.
The unknowns are, what direction it will take, whether prices stay reasonable and how host integration will develop in the future.

The integration in Rhino already is awesome and I personally would still recommend it highly. The standalone also works pretty well.
With the multiple render kernels it is usable in a very broad range of uses.
And things like bucket rendering on GPU let you render even huge stills - and there is always CPU fallback.

It also seems that the next bigger update is around the corner.

There always is a certain amount of unpredictability in everything and even more so after an acquisition, so it's hard to make solid recommendations at this point, but from a quality and price point, you can't go wrong with Thea IMO and so far Ioannis was more than fair with the users..

Cheers,

Tom