Why shouldn't Epstein shoot for 2015? The Cubs can count on huge crowds regardless. They don't have any sense of urgency to be competitive before then.
Things would be different if the Sox looked like they have their act together for the next couple of years, but that doesn't seem to be the case. If the Sox had been able to follow up their 2005 success with more consistent playoff appearance, then the Cubs might be starting to panic right now as the shift in the Chicago market became more dramatic. But this didn't happen. The Sox totally let the wind get out of their sails over the last 4 seasons and don't look to be a serious threat the next couple of years either. So, the Cubs know they still own this town even if they stink for the next few years.
IMO, it'll be 2 or 3 more years before anyone seriously starts calling for Theo's job. I wouldn't laugh off the idea that they could be playoff contenders in 2015 either. I'm not saying this out of any love for their organization or any idea that Theo is a "genius". I'm just saying this because things can turn around relatively quickly in MLB. All the Cubs have to do is get close to decent talent-wise and I expect Ricketts to open up his pocketbook and go on a spending spree to put them into the playoffs.
White Sox Baseball 2011-2016*
*except for 3 months in mid 2012 and 5 weeks in early 2016