It sounds like U2's next tour will not be until 2026-27, according to bassist Adam Clayton. The band has to first finish their next album before thinking about touring.
During an interview with Clayton on RTL with Éric Jean-Jan, he talked about what's coming next (via U2Songs.com). The band is in the midst of recording their next album in the studio. He gave a detailed answer about their plans to tour after it.
“We are recording; we are in and out of the studio. We really want to get a record of new songs to our audience,” Clayton explained. “When we know what that record is, we'll go out and tour it. I don't know which year. It may be 2026; it may be 2027.”
The first step is finding out the condition of Larry Mullen Jr., who missed the band's residency at the Sphere. Mullen first joined them in the studio at the “end of the summer,” and they recorded three or four songs from those sessions. Clayton added that they are going back to the studio in a couple of weeks, maybe even having six or seven songs “before Christmas.”
After that, U2 will finish them. Clayton seemed optimistic that they could release the record by the end of 2025 or in 2026. He did concede, though, that he is “not sure how long it will take.”
Previously, Clayton said the band would have a better idea of the album's status by the “middle of next year.” Perhaps that will still remain true if the upcoming recording sessions go well.
Additionally, Bono and The Edge are working on what the latter has described as “crazy sci-fi Irish folk music” with Brian Eno. However, it is unknown if that material will be featured on U2's next album.
Will U2 tour in 2025?

By all accounts, it does not sound like U2 will tour in 2025, and it may be 2026 before they hit the road again. If they do not tour until 2026, it will have been seven years since their last tour (which was the 2019 leg of the Joshua Tree Anniversary Tour).
U2's last proper tour was the 2018 Experience + Innocence Tour, which visited North America and Europe. It was a sequel to their 2015 Innocence + Experience Tour, which visited the same territories. In between the tours in 2017, they celebrated the 30th anniversary of The Joshua Tree.
From September 29, 2023, to March 2, 2024, U2 embarked on a concert residency at the Sphere in Las Vegas, Nevada. U2's Bono, The Edge, and Adam Clayton were joined by Bram van den Beg for the shows.
The residency was centered around their 1991 album, Achtung Baby. For the first time, U2 played the album in full every night, including deep cuts like “So Cruel” and “Tryin' to Throw Your Arms Around the World.”