I'd be much more excited about a Panther film than an Ant-Man film, but when it comes to the Avengers I'd rather see neither. Panther is just a martial artist type and there are already 3 of them (Widow, Cap, Hawkeye). And turning little just ain't that exciting.
The Avengers need someone that add versitilty like Quicksilver, Ms Marvel, Namor, you know really powerful characters that can cover alotta ground quickly. Cap, Hawkeye, and the Widow seemed to be stuck on the same street during the final battle.
Or Marvel could introduce 5 or 6 new heroes so some could be temporarily knocked outta action to make the ememy look strong. None of the heroes really got hurt in the last movie.
Maybe when the original six get they @$$es kicked Panther and Ant-Man could be Fury's emergency back ups who go and free the other captured heroes.