Marvel Editor-In-Chief Axel Alonso has tweeted a tightly-cropped illustration of what appears to be the Thing in the familiar Fantastic Four blue-and-white, but with an "2" belt buckle instead of "4." along with the words "It takes 2."
The Thing is currently operating as a member of S.H.I.E.L.D., while the Human Torch is working with the Inhumans. The Richards family has been absent from Marvel titles - and Marvel continuity - since the end of Secret Wars in January 2016, operating outside the known universe.
The upcoming Legacy one-shot has promised "the dramatic return you've been waiting for" - which the Fantastic Four would well qualify for, for many fans.
However, a possibly alternate meaning to this image could be the Thing's long-running role in Marvel Two-In-One.