I don't know exactly what the deal is in the US, but I can talk in a
really general manor.

Java is one of the most common programming languages that Universities
teach world wide. So I would guess that there are a bunch of people who
are taught how to use it.

However that being said, the more flexible you are, the more hire-able
you would have to be.

You may be in a very good  position. Java is available for the Tandem which
runs within the OSS environment. Since you have Tandem background, you
would have an advantage. I know this does not answer your question
directly but hopefully it would help your decision.