I believe (which means I don't for 100% for sure) that the new lounge will be mentioned at F checkin desks and hopefully also to Platinums at say BNE, and also that staff moving through the cabin on approach to SIN to hand out arrivals cards etc will also be advising loungeworthy passengers of the new lounge. The comms has been a focus for the SIN lounge team and I'v actually suggested to them that they take a leaf out of BA's book and have an 'invitation' slip with a pretty pic of the lounge on one side and details & map on the other that's handed out to F, CL, WP and P1 pax (similar to what BA does close in to LHR for its T5 arrivals lounge). We shall soon see if that's been taken up.
I'd certainly hate to be loungeworthy and on the QF1 or QF2 transit but not know about the new SIN F lounge until I rocked up at the J lounge, and then miss precious minutes of lounging time having to make my way to the F lounge (I mean, it's not even 10 minutes walk away, but still, those are short transits and if the flight pulls up at a C gate you're facing 15-20 minutes of lost lounge time).