The Architectural Vision will be impractical
There can be several causes of an impractical architectural vision. The architect may be a poor architect, he may have too narrow a viewpoint, or he may be out of touch with the current technology.
The topics of poor architects and narrowness of vision are covered elsewhere; lack of consideration for pertinent features in InappropriateArchitecture, size of the problem in DecisionsNotEasy, and breadth of skills and viewpoints in DysfunctionalTeam. Where the technology is completely new, this topic is covered in UnknownTechnology.
It is possible for an architect that has confined himself to architectural matters for a while to become out of touch with the technology. This may result in inappropriate architecture. Somebody, not necessarily the architect, should be keeping an eye on new technology and feeding in promising ideas for consideration. However, the architect may also become out of touch with the technology being used by the developers. This can be avoided where the ArchitectAlsoImplements. To avoid following an authority figure unquestioningly, have a WiseFool on the team.
Feeding new technology ideas into the team is still problematic, though a team using modern processes may also be early adopters of technology by their nature. However, DevelopingInPairs keeps skills current, and architecture is a shared responsibility where CollectiveOwnership is practiced.