The mixed-use movement continues to spread, obliterating old shopping malls in the process. Gateway Developers LLC has begun a $380 million, 1.3-million-square-foot mixed-use complex in Mission, Kan., to replace the underperforming Mission Center. Gateway will include 350 condominiums, 500,000 square feet of retail, 180,000 square feet of office space and a 150-room hotel project. “A mile and a half away is Mission Hill, which has phenomenal demographics,” says Tom Valenti, managing partner with Cameron Group, which formed Gateway Developers with GFI Capital Resources Group. “These are stable communities, but on the retail side of things, they have been underserved.”