Not to run on too long, but a bit more...
One of the biggest questions in my mind, as far as the future release schedule is concerned, is how they are going to fit in all of the hypothetical settings they might publish without going beyond two a year. If I were to guess, I could categorize them like so:
Huge likelihood/almost definite:
A new setting
More Magic settings
Planescape/Sigil/something planar
Significant possibility:
Dark Sun
Forgotten Realms setting book
Exandria expansion
Another new setting
Some possibility:
Greyhawk
I consider everything else--Mystara, Birthright, etc--as being somewhat possible, but not before the above.
Meaning, even ignoring Greyhawk, that's six or or more settings -- more if you consider multiple Magic and new settings. Even if we slot in two a year, we get through six by 2025, but that doesn't account for multiples, and I see them publishing at least one new Magic setting every other year, and possibly more than one new setting in that time-span. If so, that would be eight settings in three years.
Could they eventually--perhaps as soon as next year--publish three settings in a year? That seems possible, especially if they go with the "new format" and adventure-setting hybrid approaches, like we're seeing with SJ and DL.