I doubt that Sasuke needs the sharingan for the chidori, though this depends on the target. Most ninja are below Sasuke in terms of reaction, speed, and jutsu utility. That is to say, if Sasuke went running at a ninja, lets say Chojuro (because he has a sword,) with his chidori ignited and his sharingan off, I am almost positive that he would land the strike. Why? Let us discuss what Minato meant when he was warning Kakashi about the chidori.
Kakashi used the chidori on an opponent using the shadow clone technique, whose strength was thus split between all of those clones. Notice that Kakashi was able to destroy ALL of the clones, but when it came to the real body he was almost cut in half. This is because Kakashi, though powerful, was roughly the same strength as his opponent. His opponent had comparable dynamic sight, reactions, and more battle experience I would gather. Minato was essentially warning Kakashi against using the chidori against opponents that are close to the same physical level of skill as himself. This would include the likes of Zabuza, Obito, and whoever else we have seen him use chidori/raikiri on.
Let us consider Sasuke. He is very fast, and has very good eyes even when they are not sharingan. He battled Killer Bee without his sharingan activated, and only used it when Killer Bee began using his multiple swords. If it was someone beneath his skill (as most people are), I am sure they would be on the receiving end of his entire arm through their chest.
Also, another very important point is probably the most obvious. Naruto and Sasuke have clashed their techniques numerous times. They are essentially the same kind of technique (hand held, charge at opponent, aim for chest area, and hope,) except rasengan is shallower. Rasengan only needs to touch your chest, whereas chidori is meant to go through it. So the sharingan is only useful for the chidori in giving Sasuke extremely enhanced depth perception. Otherwise rasengan would also need a sharingan. Minato saw this important difference between the two techniques and that is why he warned Kakashi. He also noted that Kakashi's personality was too risk taking, and warned him as a worried teacher as well.
In short, I do not think that Sasuke really needs the sharingan for HIS chidori, because he is physically superior to most opponents. He would need it against Naruto if he actually wanted to have it penetrate Naruto (due to the above described functional difference between the the rasengan and chidori), but for clashing against a rasengan he needs the same amount of visual processing as Naruto, which I am sure he has in spades. What do you think?
