Here's what the publisher has to say about it:
Frankly, given the timing, and the implication that it will be "huge" news, there's a good chance this is tied into the publisher's South by Southwest announcement, coming next month.
Marvel #1Begin with the best super heroes in comics--Marvel does it FIRST!!
HUGE story coming soon to fans, worldwide.
If that's the case, given they're showing up at the Interactive arm of the festival and that last year's big Marvel announcement related to the launch of their AR app and digital bonus features, it doesn't seem too unlikely it could be a digital-first or digital-only announcement. DC Comics has beaten Marvel to the punch on most of the major digital steps since the launch of the New 52, so what it could be (aside from something obvious like making all their #1 issues free digitally after they're no longer new) is anyone's guess.
Certainly the fact that characters like Ant-Man, Doop and The Thing, none of whom have solo titles at the moment, suggests that it might relate to the publisher's back catalog, currently available digitally via the Digital Comics Unlimited program for a monthly charge.