No, rabbis should not be concerned with women gaining secular knowledge, and the reason is simple: It is not the rabbi's call. In this country, women are free to pursue whatever knowledge they desire. This right was hard-won, and anyone who has a problem with it is better served taking up residence in a country that still practices discrimination.
No, Ultra-Orthodox rabbis should not be concerned about women gaining secular knowledge from attending university. Ultra-Orthodox Rabbis should embrace and encourage women to gain knowledge in any form from any institution. Religious leaders should not interfere with any person - man or woman - seeking a form of secular education.
They should not worry. This is because the rabbis should be glad when their female flock gains knowledge about the world. The women will be more attuned to the teachings of Judaism when they know they are mot being limited by the figure heads of the religion. People who are meant to be devotees will stay so..
Not being ultra-orthodox myself, I don't really see where the problem is with women gaining secular knowledge. If we are supposed to have free will, and the devil is trying to tempt us, this seems like the perfect chance for people who are religious to stand up for their religious convictions, even in the face of contrasting "evidence."
This one sect is the only group of people who see any issue with it.