Prop 9 makes it unlikely in the near term, but I can see NU adding the sport sometime down the road once it finishes with the upgrades for FB and when the BB programs get on track and get their upgrades as well.
As much $$ as NU gets for its share of the B1G take (which will only increase), there is no reason for NU to only offer 19 varsity sports when schools like Stanford and Duke offer a good bit more programs.
With the B1G likely adding a payout for schools that have lax programs (like it will be doing for the schools that have hockey programs) and NU already having the lax facilities in place, it would be much easier and cheaper for NU to add men's lax instead of say, hockey (can add women's crew to balance things out which will help the men's club program).
Lax is a popular and growing sport in the NE region - which has the biggest concentration of high achieving students that NU is competing for with most of the top high schools having lax programs.