The Glen
Legend
I don't think WoTC will touch Mystara. The community is really attached to BECMI and they already do a very good job with the Threshold fanzine. The risk of doing it a disservice is too high. Letting Goodman Games do the Basic modules reprints with 5e adaptation is a far as they will go.
I think a lot of the Old Guard would be happy to get new material for the setting regardless of the format. Though I think wizard would be more inclined to try to make it somehow like the Capcom game because that was so successful. The biggest issue would be Wrath of the Immortals because that broke the setting in the fact that the materials printed after that box set didn't sell well at all. They might just go from the 1000 time line and pretend WOTI never happened.