Many assume CBC wants to continue with the arrangement, and there is the possibility that they don't want to or would carry fewer games. If they are part of any deal, the playoffs and Stanley Cup would always be included.
CBC doesn't get any of the revenue from the games, but it doesn't cost them anything either. Also they get a lot of free promo on Rogers for their programming which is valuable to them.
One big disadvantage that CBC TV has is the fact they don't have many ways beyond their TV channels to promote programming. Rogers, Global and CTV own a large number of radio stations and specialty channels that can hype the TV schedules all day long, 7 days a week. CBC radio has very little time to promote shows from the TV network, and CBC doesn't own many specialty channels, so the time on HNIC is important.
Rogers owns City TV, and OMNI stations so the Stanley Cup finals could always end up on those channels if CBC was not part of the plan.