Delta is bringing major upgrades to Boston with the opening of a brand-new Sky Club Express, expansion of the existing A18 lounge and introduction of a new shuttle bus service for connections.
thepointsguy.com
Delta is planning on building a 20,000 sqf SkyClub in terminal E that will open in summer 2023, which should coincide with the terminal E expansion opening. I'd imagine all SkyTeam airliners - KLM, Air France, ITA and Korean, will use this club. This would put it on par, size wise anyways, with the much lauded SkyClub Delta opened in Seattle a few years back. I believe this will be the largest club over in E. The Lufthansa, Emirates, and British Airways lounges are in the 12-14k sqf range.
The remodeled and expanded SkyClub in the the A satellite is done and doubled the seating capacity.
The article also talks about the buses Delta is running between A and E. Seems like a pretty quick option for those connecting.