In a recent article published in Renewable and Sustainable Energy Reviews, the challenges for the future of off-shore wind were discussed, considering Spain as a case.
The need for floating structures is a clear cornerstone for the development of off-shore wind in countries like Spain, where swallow waters are not convenient or restricted.
The development of these technologies to a commercial level will bridge the difference from on-shore connected windpower and off-shore or off-grid generation. Energy harvesting as discussed in this post with multi-use offshore platforms can be envisioned as a next step.
Excluding the technological and environmental challenges, there are other hurdles.
As it is highlighted usually, the unstable regulatory framework causes a lack of interest for investment, specially if paired with complicated administrative procedures.