What's interesting to me with people heading over (or back over) to M:tG, is that it implies they don't anticipate a need for much full time staff for D&D after the core books are out. James Wyatt seems to be finishing up his job and then being reassigned so WotC can use more or less the same skillset elsewhere.
I wonder if they are going to call on a lot of freelance work for additional D&D products? With the focus on adventure paths and limited rules expansions, it makes sense that they can get by with less people dedicated to R&D and content creation.
It also makes me wonder if some of the designers that left simply got offered some good opportunities elsewhere, and chose to take them because theyk new the D&D team was downsizing after 2014, and didn't want to risk being part of that downsizing.