Marvel vs. Capcom Fighting Collection: Arcade Classics and Capcom Fighting Collection 2 aren't skipping Xbox anymore, with ports confirmed for 2025. This will be sometime after the Marvel vs. Capcom collection launches on PC, PlayStation, and Nintendo Switch, however, as the devs work through technical difficulties.
Capcom confirmed this just now, saying that the ports can be made after it engaged in "discussions" with Microsoft. This comes after it was suspected that Xbox was skipped due to issues with Capcom's MT Framework engine, making game ports too difficult to justify.
We don't have a specific release date for either port, other than they'll both be coming to Xbox One at some point in 2025. This is also the only release window we have for Capcom Fighting Collection 2 on any platform, but it is long after Marvel vs. Capcom's launch on September 12.
Shortly after it was speculated that Capcom was skipping Xbox over these engine issues, it was reported that Microsoft was "actively working on" a solution with the studio. It seems that this was accurate, given Capcom's wording here, and that the two parties have come to some kind of agreement.
We'll have to wait and see how...