Chained Prometheus
The Spiral King
Another way too early to go, but I am anyway:
Perhaps Bruce wants to tour (and not just a few gigs) right after the release of his solo album. If that tour doesn't fit in Rod's/Maiden's plans, then perhaps Bruce/Roy Z have decided to wait with releasing the album until a better moment to tour arrives.
I could see this being the case. My guess is that since Bruce pretty much put his solo career off to the side once he rejoined Maiden (aside from recording Tyranny of Souls), that he wants to give it his full and proper attention once Maiden retires.