Growing a complete, functioning brain is unfeasible, but there is real potential in growing functional neural tissue containing specific types of cells, for transplantation into the human brain.
It may not be possible to regrow a complete brain but we may not have to. If medical science was able they could potentially regrow certain cells and parts of the brain that have degenerated that could prove to cure certain diseases like Alzheimers.
A study is being done in Japan that has regrown a pituitary gland that is fully funtional when it was transplanted into mice. How soon will it be before it is done on humans? Or is it already being done?