There is evidence that it is. They have been able to record images people are seeing from fMRI data. The information is there, it's just a matter of processing it.
Right now, researchers are putting together functional brain structure maps combining fMRI, SPECT and PET scans for Alzheimer's research. Apart from the inconvenience of wearing a giant magnet, pulling together one or more brain scan techs with compute resources might be a way to pull it off. Heck, if the compute power needed were too bulky to be practical, it might be possible to offload it to a hosted service. (Talking a solution 15-18 yrs out anyhow.). It's entirely reasonable that keyboards would be slower than thought input in 50 years.