‘Sunrise’ isnt falling over if Sydney- London becomes too difficult.
Is sounds like the first two routes are LAX and JFK at this stage, with SYD-LHR not on the cards until well into the second or even third year. PER- LHR after that. Obviously that could happen first if Direct from Sydney is unviable at the earlier point. Then it sounds like other routes to the Americas such as Dallas and Chicago are being considered. No other East coast to London (at the early stages anyway).
The first aircraft isn’t due until mid 2026. So it won’t be until towards 2028 that Syd-LHR direct would be happening. A lot of water under the bridge between now and then in any case.
There’s plenty else the 12 ULR configured aircraft can do instead.