This year we're getting the new Marvel Battlegrounds play set for Disney Infinity 3.0 so there will be new marvel characters.(All the previous marvel characters are playable in the new play set.)
In 2015 the guys at Disney said that there are 4 more characters left to be revealed after revealing Hulkbuster and Ultron at SDCC 2015.
in October at NYCC 2 characters were added to the list of marvel characters Captain America The First Avenger and Symbiote spider-man but they were not part of the 4 unrevealed characters.
A month later a picture of 3 unrevealed marvel characters leaked they were Black Panther, Ant-Man, and The Vision but there was still one character missing.
here's my theory Disney Infinity 3.0 play sets have been coming with a female and male character so the marvel play set should probably be the same, the guys at Disney said that the new captain america figure will come with the play set along with another character that i think is scarlet witch because the new marvel characters are inspired by the marvel movies (Captain America Civil War and Avengers Age Of Ultron.)
the new marvel battlegrounds play set will be available in March of 2016