If they were playing Europe and Radio City in September, i'm pretty sure the shows would have been announced by now. Financially, they wouldn't make any money taking their show over to Europe for only a handful of dates. Seems very unlikely to me.
It would have to be late next summer at the earliest, with a scaled back production. They could do a mini run in London and Germany to keep travel costs down, then bang out 4 big shows in NY and LA to nail down some profit.
If scaled back, would need multi dates per venue to keep travel costs down and easier on the band. Say two shows in Cleveland. Need 2 or 3 dates in NY and LA each to bang out some profit. The larger the show count, the unlikelier the dream.
Lifeson did cite Gilmour's most recent 18 show mini tour as example. Gilmour did play many venues smaller than arenas if I recall correctly, so there's a way to do it financially. If they are healthy, there is some hope.