Yeah, Russell probably is a starter in major leagues in 2015 for a number of organizations.
Could be with Cubs too but other things might have to happen with other guys:
... if Bryant doesn't look good at 3B and moves to OF, opening for Russell.
... if Baez struggles with contact issues and isn't starting in majors, opening for Russell.
... if Cubs look to make mid-season major trade (Hamels?) and ready to deal Castro mid-season, opening for Russell.
... if a starting IFer gets hurt, opening for Russell.
... if Cubs are clearly a 2015 contender by mid-season and brass feels that Russell in majors in some capacity clearly improves the club for a post-season run, opening for Russell. For service time issues, don't see just a September call-up for Russell. If he comes up, likely would be much earlier.
Otherwise, possible scenario is that Russell situation is a 2016 redux of Bryant/2015: a few weeks back in minors for service time issues and an early 2016 call-up.