Considering an internal offer to change focus from Java to Groovy. Would this be a good move?
Where would I ask a question like that?
There is no good place on the Stack Exchange network for this kind of question - it is much too specific to a single person (so will not be of use to others, which is something that is desirable in a question).
It is also very open-ended - this is also not wanted.
There is a place to ask workplace related questions, though - The Workplace, though this would be off-topic there as well.
You could try one of the chat rooms in chat.SO. There are likely to be many people with advice to offer.
I don't see any Groovy rooms, but there are plenty for Java. Just stay away from: Java Sucks - Suffocating from the stench of a thousand cow farts... Their opinion is likely to be biased.