Terry Collins and the Mets return to Citi Field Friday night to begin the final homestand of the 2017 season with an uncertain future. After seven seasons at the helm, the Mets manager’s contract expires after this season and there have been no talks to extend his tenure. Team sources said privately they expect the 68-year-old to retire. Collins, however, reiterated this week that he has not decided his own future. Nor have the Mets told him their plans. The only decision that has been made is that Sandy Alderson, whose contract also expires after this season, will be back running the team next season, according to multiple sources. Collins is the only manager Alderson has had in his tenure as the Mets GM.