Declining enrollment in CIS during the past 3 years is influenced by a number of factors. The first is that it is one of the hardest of the engineering majors, and that may turn away some engineering students who feel that they cannot make the upper level grade of engineering. The second is state of the economy and job market. Tech companies are not flourishing as they were a few years ago, and so the field is oversaturated. There are constant stories in the newspaper on how computer engineers are out of work because their job was shipped to India. I believe the field will eventually balance itself out, but until then it will suffer with an over saturation of computer scientists. .
In order to get high ranking high school students into the program, computer science courses need to be available in all high schools. By this I do not mean classes on word processing, or how to use windows, as those were the classes present at my HS. High schools should have a computer hardware course, and a software programming course, in order to give its students a taste of what computers is really about, not just surfing the net. I also think that the CIS department would be able to recruit undecided engineering majors if they were to have speakers/demos on the interesting things you can do with CIS knowledge (speakers on programming games, or writing programs for personal use). .
Personally I think this decline in the amount of CIS students is the major balancing itself out after a spike in the amount of work needed. Now that programmers are not in such high demand, students who desire to be in CIS for the interest of computers will do so, and not just because programming firms are offering BMWs as signing bonuses. .