Latino Review is reporting a rumor that Marvel is developing a series of 10-minute short films to introduce secondary characters like Black Panther, Luke Cage, Iron Fist, Dr. Strange, etc. No other information is known at this time, but this would definitely be a much less costly way to introduce perspective new franchise characters without investing tens of millions on a feature film. Through these short films, it would be easy to see what is connecting with audience.
Nothing is confirmed yet, consider this a rumor for now.
We are unsure if these short films will be released online or be attached to future Marvel big screen releases. Pixar seems to have brought back the concept of short films before theatrical releases. Disney has even picked up the practice. Recently it was announced that Warner Bros would be producing a series of new 3D Looney Tunes shorts to be attached to future releases. (Thanks for the tip Don!)