For gameplay and longevity reasons I'm glad they're going for procedural maps like normal.
But I wouldn't mind having tonnes of prefabs either. Strategically it might be good to be able to rely on having certain prominent terrain features to help you defend or attack in certain places. I know proc-genned maps will stay the same in each battle at those co-ordinates, but prefabs tend to make for quite nice and specific challenges to overcome or utilize.
I wonder if the proc-genned ones have been massaged a fair bit to suit different army types? Will the traditional dwarven areas suit turtling while the bretonnian areas have vast plains with a few forests suited to cav charges, whereby giving a racial hat and reason for those people to live there and be successful in those places? Or will these map types at least be more regular in "their areas"?
I guess there'll be a bit of both, so you probably will learn where better places are to engage, depending on army makeup. You'll probably find you own "Blackfire Pass" that suits your army type and playstyle every once in a while, and note it down for future reference for defenses, while certain other areas will have prefabs with really well detailed pre-canned maps. Ever easy to please, I want stacks of everything, and for it all to be done really well.