Globe article today on Delta's growth at Logan: https://www.bostonglobe.com/busines...gan-airport/ckthglHJBmIJlXcdnKITDJ/story.html
Their peak daily departures were 117 a day in 2018, they're aiming for 141 this year and 158 in 2020. Pretty significant growth there. No news on where new destinations will be, though.
My guess is there will be another European Destination for Summer 2020 - (maybe Shannon or they take over Manchester UK from Virgin), Dallas-Fort Worth, and from previous posts Burlington VT or Rochester NY.
They may consider Grand Rapids MI, Madison WI, Omaha or Louisville at some point with an E-Jet or even A220.
San Antonio would be a good A220 route.
I've heard they struggle on SFO but they may need to go to 3x on it.