The sequel to Ant-Man, Ant-Man and the Wasp, was announced earlier this month by Marvel to be a part of their Phase 3 lineup. The studio is now in negotiations with Ant-Man director Peyton Reed to return and direct it.
There is no info yet on what the sequel will be about, but Paul Rudd and Evangeline Lilly will return to reprise their roles as Scott Lang, aka Ant-Man, and Hope Van Dyne, aka The Wasp. Their adventure may or may not include Janet Van Dyne. Marvel Studios president Kevin Feige has said in the past that there are stories with her in them planned for the future.
Ant-Man and the Wasp is scheduled for release July 6th, 2018. Keep a look out for more information about the film as the date approaches.