When discussing the final days of Picard, Stewart was quick to point out that Star Trek: Nemesis was not a financial failure. "It didn't lose money. It simply didn't make as much as all the others." He also said that Nemesis writer John Logan told him that "somewhere out there" there's an outline for a script with "all of the Star Trek cast members in it" that we'll never see. No, he didn't elaborate to say if that meant Sisko and Janeway and Archer, too. You'll just have to imagine and argue what in the heck that could possibly mean.
what we already knew:
An eleventh Star Trek movie was initially planned during production on the tenth film, Star Trek Nemesis. Nemesis co-writers John Logan and Brent Spiner intended to follow that film with a "crossover" sequel. After Nemesis failed financially, however, this plan was abandoned.
my guess is it wouldve been like an Avengers movie of all the Berman spin offs and had members of the TNG/DS9/VOY casts along with the ENT cast (as it may have been a time travel film) and maybe even some of the original cast (Sulu? Chekov? Spock cameo?)
maybe something along the lines of IDWs Last Generation or the Bring Back Kirk trailer but without Kirk