I think they might be burnt out from Central/South America after TAR 35.
That said, since Cologne was visited apparently countries from 34 are fair game to be revisited. I doubt France will host a leg due to the riots (even if they are currently winding down) and another penultimate leg in Iceland would be a little too soon...Spain perhaps? The last two times they stayed in Andalusia but there's still Barcelona, Pamplona, Madrid, Basque Country, etc etc. all of which can connect to the US pretty easily.