For Squid01, as of now, the QF J lounge and the QP at ADL are combo, and as far as last Dec, no works have been started, so you are not missing out.
I don't think that any major works would have started, if they expect to finish it that fast, ie, by your flight date month of May.
Goss on here is the works in relation to ADL QF lounge is not visible, not sure how this is so, ...
I have flown out of ADL with QF a lot in the past, over the past few years, and have not seen any visual changes in relation to the QF ADL lounge, unless they are in a tie in with the Plaza Premium lounge after immi downstairs.
Plaza Premium, as Sww199 mentioned, is newer, if you want to try a lounge esperience.
As you are a QP member, you will know what the QP ADL is like, and as QF J flier, I can't see the difference between the two.
If CL is in equation, then yes, that would be a +++.
But for ADL QP and QF ADL J lounge, no difference.