You need to be more specific. Thrive in what context?
I think Scala's community is near the critical mass that it needs to be a self-sustainable open source project even if its primary institutional backer, the EPFL, suddenly had a change of heart; and there is currently every sign that it will reach this critical mass. I think Scala will be with us and actively maintained for a long time.
A more pressing issue if the type of uses for which it is suited. The Scala compiler and standard library are far from perfect. When you start pushing the language or a portion of the library there is still a decent chance that you will find bugs. This is improving by leaps and bounds, but it in itself isn't the core of the problem.
The problem is in order to get fixes you pretty much have to upgrade to the next version of Scala as upgrades come out. The problem with that is that most version upgrades contain breaking changes, thus in order to obtain fixes you are likely to have to change your own code. There's also the binary incompatibility problem, which means all your Scala dependencies have to change versions, too.
This could be severe problem if you have a lot of dependencies on other Scala libraries (unlikely - there aren't many yet), if you are subject to severe infrastructure bureaucracy, or worse, you're a product-oriented company that needs to distribute fixes to customer with severe infrastructure bureaucracy.
In order for Scala to be viable in such situations long-term, someone will have to start back porting fixes to earlier versions so that people don't have to perform breaking upgrades just to get some fixes. I'm sure this will happen, because it really wouldn't be that hard, but it will probably require someone seeing a business opportunity, because let's face it, backporting changes and doing regression testing isn't exactly exiting work.