The original proposed stations were Washington St, Gilman Square, Central St, Lowell St, Ball Square, College Ave, Winthrop St, North St and West Medford.
There is some controversy in Medford as to whether the line should go all the way to West Medford, mostly around traffic and parking issues. West Medford sees a lot of traffic already, and they don't want lots of commuters driving in and parking on local streets. There's also the persistent misconception that the line would have to cross Rte. 60, adding to the backups caused by the commuter rail crossing. The DEIS for the project described the line as ending at Winthrop St, by Tufts. A group called the Medford Green Line Alliance is calling for the line to end at Rte. 16, by the Wild Oats, and combine the College Ave and Winthrop St stations into a single station halfway between, across from the Tufts police station.
I think it should go all the way to West Medford, not least because that would enable transfers to the commuter rail for outbound commuters.
Meanwhile, there are some people calling for a stop on Cedar St, supposedly to serve Magoun Square, instead of on Broadway at Ball Square, which I think is a terrible idea: that location isn't actually any closer to Magoun Square than the Broadway location, and doesn't serve Ball Square remotely as well. (I live near Ball Square, so this is of personal interest.)