They have already separated from MCD on the most expensive items anyway - meat. Natural-raised pork, beef and chicken. Where else (except Coke) does MCD offer superior pricing advantage? Tortillas? Rice? Beans? I don't think so.
I see this as a non-issue.
I like to focus on this - "Chipotle is looking to up operating earnings by about 25% per year over the longer term based on a combination of new-store openings and strong margins. This year, Chipotle forecasts a the mid- to high-single-digits rise on a percentage basis." - CBS Market Watch.