Can assume the GBL tour will likely be 5 weeks Oct-Nov.
Ausx3, NZx1, and x1 vs a Pacific Island team, lets say Tonga.
Aus will probably play 1 more game v NZ before this.
I wouldn't expect Australia to play any more games, certainly not a tournament.
We could expect NZ and the Pacific Islands to be available for a tournament.
England and the home nations are a much trickier ask.
The home nations will be involved in WC qualifiers and while they could organise the calendar in a way that fits both it seems extremely unlikely.
England playing at the same time would raise too many credibility questions to be worth it. Maybe we will see another England Knights showing.
Italy and France will be deep in WC qualifiers.
All other nations will be involved in WC qualifiers and don't have the professional players required for a top tier tournament anyway.
That leaves Lebanon.
So in addition to the GB tour and WCQs, we could reasonably expect to see either:
A) probable...
4 team pacific cup (PNG Fiji Tonga Samoa).
+ NZ standalone tests vs Tonga and Samoa
+ Lebanon standalone tests vs PNG and Fiji
B) some form of 6 nations tournament with NZ, Tonga, Samoa, PNG, Fiji, Lebanon