is possible but impractical;
will supersede organic intelligence.
These are possibilities considered by Poul Anderson. Jerry Pournelle & SM Stirling suggest a fourth:
conscious computers quickly go insane.
This might be because a consciousness able to think in nanoseconds and to control its sensory input prefers to make a universe that will last subjectively forever in a few objective milliseconds.
In Anderson's A Circus Of Hells, an abandoned conscious computer alone on an isolated planet for five hundred years plays robotic chess and war games in order to preserve its sanity. Thus, it is moving in the direction of Pournelle's and Stirling's AI's.
Anderson covers nearly every possibility.