I've seen it suggested that this is misdirection. That yes, Angela is going to appear briefly in the Marvel Universe, and they're announcing this now so that we don't notice that there's something else happening. While I don't think that Marvel is that
clever, if so, the only thing that would be bigger than Gaiman bringing an Image character to the Marvel universe would be Marvelman.
And given that Gaiman has been a driving force in getting the Marvelman situation squared away (1602
a decade ago was part of that effort), then I think that it's at least possible
that Marvelman will finally
show up in the Marvel universe.