The word "never" does not exist in a scientists vocabulary. Will Wright (see biography here) stated that "Machines will never achieve human intelligence." I believe this to be a strong assumption. Mr. Wright further states, "Intelligence is whatever we can do that computers can't." See the text and video of the interview on Popular Mechanics here.
This has rekindled a long standing discussion with Franz Dill again, see his post "Prophecies about AI" here.
Computing is currently limited, yet moving at exponential speeds (in gaining speed). As soon as the silicon wafers in integrated circuits are replaced with diamond wafers, we will have a factor of 10 increase in the ability to withstand heat in an IC. What does this do to speed? Currently the science has pushed the existing formula (in practice) to roughly state that (in CMOS based technologies) the heat generated by a processor is approximately proportional to its clock rate, see detailed paper here. So Tera-Hertz is not far.
With such speeds more data processing occurs faster. Generically speaking, human brain stores all, applies patterns of learned behavior and hence the decisions - the key to move from one node to the next in the decision tree, or jump, or, etc. With increase in computational speeds, machines could be preloaded with "human" patterns - resulting in human like decision making. Excellent primer on human brain functionality here.
Yet, with Quantum Computing and organic memory storage and processing available one day... I have to go back to the word "never" as stated by Mr. Will Wright... I am tempted to say that there is never such a thing as never!