Betts, Bogaerts, and E-Rod have shown really well at the major league level. Swihart did have the injury setback, but he leapt to the majors after very little AAA ball and has kept getting better. Moncada and Devers are going to move quickly, watching them you can see they're more Betts than Bogaerts.
Sam Travis (1B) will also force his way into the majors early next year. The one big organisational weakness is starting pitching, and their major league scouting department is so bad I find myself secretly hoping that they don't address the problem in free agency. Anderson Espinoza will be pitching in Boston sometime in 2017 (despite their best efforts they won't be able to stop him, at 17 he's dominating 19 & 20 year olds), albeit on a limited schedule. Boston's amateur scouting department is as good as the MLB one is bad. It's bizarre.
EDIT: Moncada and Devers are the interesting ones, because they're both IF and Boston has players everywhere but 1B, and they have Travis waiting in the wings there. One of those guys is probably going to LF (Devers most likely). But after next year I expect that Boston will be subsidising Sandoval's contract to open room for Moncada.