I could see the movie going something like this....
Antman invents ultron, ultron goes against him.
Ultron invents vision who then goes against him.
Leaving the final battle to be antman and vison vs ultron, where they defeat him (cause ultron one isn't that powerful.) Then ultron comes back stronger than before in avengers 2 and fights the whole gang.
That would be cool. And we all know hollywood loves crazy, killer, lazer beam robots. And it would two more people to the avengers team.
How about an Antman movie like this...
Antman invents Ultron, slaps wife. Ultron kills him.
Ultron invents Vision, who then goes against him.
Leaving the final battle to be Vision vs Ultron, where Vision defeats him. Then ultron comes back stronger than before in avengers 2 and fights the whole gang including Vision, who joins the Avengers.
The working title of this Antman movie would be "Behold... the Vision.", shortened to "The Vision" for release.