Can we enter data at the speed of thought?
I am unfamiliar with such research. However, considering this from a User Interface design perspective, as well as from a cognitive perspective, I would add one bit of clarification to the question.

Can we enter data at the speed of organized thought?

If the limitations in user interface technology are overcome to the point where the input gate is no longer the limitation, it is quite possible that we would discover that our thought processes are so chaotic as to render the new technology virtually useless.

As support for this I would point out that sitting and typing a message, while slow, is already a method by which thoughts evolve into lucid communication.