It's not really a "trial", it's an almost-finalised (in theory, at least) version of Lr, released in order for users to shake out any final show-stopper bugs not caught by Adobe's testing - hence RC ("Release Candidate").
When Lr 4.1 final is released, the RC will prompt you about the new version next time you open it, and you can then update to the finalised version.
As an aside, I can't find anything definitive about 5D Mk III mRaw/sRaw support in Lr 4.1 RC2.