Johnny passed this link on to me, very -VERY- important discovery in terms of uber-computers, the kind you'd need to run something like the Matrix.
Well, it appears that Braingate Technology (see earlier posts in HiTech) is working on a computer/brain interface with some success. And technology is moving forward at it's usual rate... It is really hard to say.
Kevlar once mentioned a direct neural interfaced computerized virtual reality would be possible within 50 years.
Keep in mind you could have something goggle/trode based much sooner than that. I would say within 25 years or so? Perhaps?
The largest stumbling block, in my opinion, is commercial viability.