A possible merger of Burger King with Canadian coffee-and-donut juggernaut Tim Hortons has been in the news. What is interesting is that Tim's doing the buying. The merged company would be Canadian-based, letting the company pay lower Canadian tax rates on international earnings; such "inversions" are the bane of American economic populists, but are an indication that US corporate tax law leaves a lot to be desired.
I'm not sure if there are too many synergies, but there is a potential avenue for combined BK-Tims stores, where the morning-centric Tim Hortons menu would fit in with a lunch-centric BK menu. Tims does have soup and sandwiches to supplement its coffee and pastries, but lunch and dinner isn't its strong suit. Some Michigan Tim Hortons were running co-ops with Coldstone Creameries, but the Wilder Road combo in Bay City saw the Coldstone side close recently. BK might be a better partner for co-op stores.
Wendy's owned Tim Hortons for a time, but didn't seem to have a handle on what to do with it and spun it off. BK management might be well-served letting Tim Hortons do its thing and limit the meddling to any co-op stores they might open; Yum has seen some success with combination stores, like a very busy Taco Bell/KFC/Pizza Hut troika near downtown Tampa that I recall from a sting working there.