The Boston Skyline is on track to change by 2020. It will introduce some new players to the top ten and maintain some existing ones.
Curbed just posted a map of the 10 tallest buildings it expects to stand over Boston in 2020:

Credit: Curbed
- 200 Clarendon
- Winthrop Square Tower
- Prudential Center Tower
- Four Seasons Hotel & Private Residences One Dalton Street
- Millennium Tower
- South Station Tower
- Federal Reserve Bank of Boston
- One Boston Place
- One International Place
- Boston Harbor Garage tower
You can read more about the 10 buildings on Curbed, Boston.