i feel like whatever is "next" is going to be the end phase for them. i'm not saying that's just one album, or even one tour. but i can't see them putting out a new album, touring, and then coming back and spending another 4 years waiting for the next phase - which would put them into their 70s.
so this last phase - the last U2 era if you will - will likely contain multiple "things" and will take place over the next 4-5 years - and by 2030 that's pretty much a wrap.
i think we see two new albums - the new one and the "last" one - whether that's still Songs of Ascent or some version of that we'll see.
we'll probably see one more career spanning compilation/box set that includes some unreleased shit from over the years - probably not full on Tracks style (definetly not full on Tracks 2 style) - but probably closer to The Complete U2 release we saw in 2004 that contained an album of unreleased tracks, or the Reassemble album.
touring - i think we'll see stadiums in Europe right away as a "make good" for Sphere. perhaps some limited stadium shows in the US as well as part of it - but more likely we'll see arenas in the US. i do think they'll return to Sphere with the full band at some point. maybe as a last hurrah type deal - tied to that career spanning compilation i mentioned.
and by Earth 2030 - when there's 3 of us left here at Interference - the band will officially retire.