It never matters how long I wait, it always turns out that if I'd waited a bit longer, I'd have got something better.
That said, my TV may have been a better buy than I thought. I might be wrong, but I now understand the trial currently only appears on Panasonics, and only those that will show HLG. That would suggest that my TV, while not conforming to any particular HDR tick box, may yet be capable of getting some kind higher dynamic range using HLG. Its a cx680 series, fwiw.
The UHD/HLG preview does look absolutely stunning, breathtaking, and various other superlatives. But it's wildlife scenes from Planet Earth, that look already pretty stunning no matter what hardware you view them on.