I take it that by "tenth member" you're referring to baseball only, BP. In that respect, yeah, the CCIW has plenty of associate members who only participate in one or two sports:
|Concordia (WI)|| wrestling|
|Dubuque|| men's lacrosse, women's lacrosse|
|Milwaukee Engineering|| wrestling|
|Rose-Hulman|| men's swimming, women's swimming|
|Washington (MO)|| football (beginning in 2018)|
... so it's possible that the league could opt to do that for baseball as well.
Each of the CCIW's six associate members has a baseball program, and each is already playing in that school's full-membership league: NACC for Concordia (WI), Milwaukee Engineering, and Lakeland; IIAC for Dubuque; HCAC for Rose-Hulman; and UAA for Washington (MO). The interesting thing is that the UAA only has seven members that have baseball programs -- Carnegie Mellon doesn't field a team in this sport -- and two of the seven choose not to play in the UAA for baseball. The league, for reasons unknown, allows them to do that. As Jim mentioned, Chicago is one of the two; the Maroons play an independent schedule. The other UAA stray, Rochester, plays in the Liberty League. One can hardly blame those two programs, as the UAA's tournament-based league schedule makes the league an odd duck in the D3 baseball world.
If the CCIW were
to add an associate member for baseball, Chicago would be a natural fit. Nobody likes the headaches involved in scheduling as an independent, and the CCIW is a solid (albeit unspectacular) baseball league. From the CCIW's point of view, the Maroons are a competitive program based well within the league's geographical footprint, and you can never underestimate the cachet involved in getting an academic institution as high-powered as the University of Chicago into your circuit, even if it's just for one sport. But the CCIW, if it were to seek a tenth baseball program, might decide instead to give Wash U first right of refusal out of courtesy, since the Bears are already a nascent associate member of our league for football, and the UAA does not have an automatic bid to the D3 baseball tournament.
If, however, what you meant in asking if the CCIW will add a tenth member is whether or not the CCIW will add a tenth full
member, the league's presidents have said that they're not actively seeking that. The league's needs seem to be amply met for the most part by having associate members in various sports in order to get the CCIW up to the seven-team minimum required for autobids to D3 tournaments, and if the nine-team sports in the CCIW want to follow the lead of football by adding a tenth for scheduling purposes, the CCIW could go the associate-member route in those sports as well.