Hey Lukas,
the norm for this route is over 4 days, though it is possible for a strong, fast and well prepared group to do it as you have proposed. Fair weather and the snow/ice conditions will naturally play also a big role in determining whether you can pull it off or not.
For some additional info on Corner Pass, including a pic of last winter's conditions, see this link:
http://vertical-endeavour.com/forums/drakensberg-passes/86-corner-pass.html. Soft snow in the gully is one thing, but if you encounter hard ice on the main crux and the short chimney right at the top, it could get really challenging and maybe even impossible without equipment. Given that it will be late winter then, the chances of encountering frozen snow-melt are good. The bottom of the pass is not that great for pitching a tent, though you'll find a spot eventually.
Bear in mind that you will not have a lot of time to enjoy the area over 3 days. The top is spectacular, especially the spine-tingling view right on the edge, looking over the Triplets. The summit cave is one of the finest escarpment caves and is well worth the visit. You will wish you had more time up there. If you have the luxury of taking 4 days, rather do that, and take on the challenge of doing it over 3 days some other time.
At the very least, keep a fourth day as a spare in case you encounter difficulties. The route has some fairly strenuous parts that may easily be underestimated (besides Corner Pass and the slog up the Trojan Wall from there). The climb up from Fergy's Cave to Centenary Hut will get you breathing hard, Leslie's Pass is not technical but pretty steep (make sure you don't loose the trail at some key points), and you'll be doing lots of boulder hopping and river crossings from the bottom of the pass to Marble Baths Cave.
It's very hard to predict what the conditions will be like, though expect savage winds at some point, if not the entire time

. The area is very high-lying, so good chance of snow on the ground on top. How much is hard to say. Check the weather report shortly before the time for any major fronts and snow warnings, and re-assess as needed.
Above all, have fun, and please let us know how it went!