I agree with you overall but the sad state of Scala's build tools make it still "up-and-coming" in my eyes.
I surely can predict that in 5 "light" years C++, even C, will not become obsolete. I know of a very innovative company which still uses almost exclusively Visual C++ 2008 (they do some heavy image processing and OCR).
Pedantic point: Light years are a unit of distance, not time.
>Is this likely to be around in 5 years from now?
In 1997 when I graduated, career services told me to erase Java from my resume and replace it with "Borland C++ OWL 2.0" so that I could land a job. (http://en.wikipedia.org/wiki/Object_Windows_Library) At that time, Java = dancing duke on netscape navigator. Right now, I'd give a million dollars to find another OWL 2.0 developer ( ok not a million, maybe $10 )
>5 years from now is it likely that this is going to be a marginalized technology
5 years == light years in tech. Nobody can predict that far out.
>it can be very painful down the road.
If you future-proof yourself by only using the most stable, well supported toolchain, it can be much more painful down the road when you are stuck with some legacy platform nobody is willing to code in because everybody has moved on to the next big thing.
>you could replace it with Scala, or any other up-and-coming language
There should be a statute of limitations on when you can stop using "up-and-coming" w.r.t a language :) Seriously,Scala has been around in some shape/form since 2003. We've had stable releases since 2008. At this point it is no longer "up-and-coming".