Delaying it to get one over on the competition sounds like BS Console Wars stuff rather than reality. Microsoft and Sony don't think that way, they're not plotting schemes against each other like this.
Whatever schedule MS has in place for releasing and distributing dev kits has surely been in place for a long time. Whether they're meeting that schedule or not only MS know.
LTD: PS4 - 125m, Switch - 110m, XBO - 51m
2020: PS4 - 9m, Switch - 22.5m, XBO - 2.5m, PS5 - 4.5m, XBX - 2.8m