lol, no resources. If Microsoft wanted it they would have 'found' the resources and handed the job to another studio if 343i were busy. Although i'm not sure when will 343i will be less busy to do that that now after Halo 5 has shipped and before they go knee-deep with Halo 6.
Taking into consideration Spencer's previous remarks they don't seem as interested in porting already-released Halo games so we'll probably see Halo 6 and on-wards on PC. But i suspect not having the series on PC is going to hurt potential sales from players who don't want to jump in the middle of the second trilogy. But with the UWP thing it doesn't seem like maximizing success of an individual game is their first priority.
I'm sure there are probably a lot fewer resources available after the bath they just took with Fable Legends.