Over creative differences director Edgar Wright of Scott Pilgrim Vs The World fame has left Ant-Man, his Ant-Man. Wright has been developing Ant-Man for about 8 years, has chosen the cast and has re-written the script over the years multiple times for the new technology that's come out. This is tragic news for fans of both his film style and a greater Marvel cinematic universe. It's hard to believe that with Guardians of the Galaxy coming out in August with such humor in its base that something about Wright's film could be disparaged by Marvel.
Marvel is still going on with the film at this point, which makes ant-sized sense.