I'll wait to see what they do with this, but I'm hoping it's some kind of fake-out. My initial reaction was displeasure.
First, Majors' legal issues aside, I thought they should have just recast Kang. If there's any character that can be recast in the Marvel Universe, it's Kang. It's a great villain and I hate to see them abandon him that quickly.
Doom, obviously, is maybe the best villain in Marvel's rogue's gallery, and I'm apprehensive about him being thrown in this way, changing horses in mid-stream.
The irony that they are recasting Iron Man as Dr. Doom because they didn't recast Kang is king of amusing.