In my reading on the subject...
The 'upgrade' to the Panama Canal, which will allow triple the capacity, is about a year behind schedule. Might be done by 2016.
The newly installed locks will be to either side of the existing locks, but are still narrower than some of the largest cargo container and tanker vessels currently in service. The new locks will be 180 feet wide. The existing canal locks are only 100 feet wide.
There is some question as to whether a U.S. Supercarrier could traverse the new canal. while the hull will fit, the 'wings' underneath the flight deck are wider than 180 feet... Most modern supercarriers have about a 134' width at the waterline, but exceed 250 feet at the height of the flight deck. A 2008 U.S. Navy article mentioned that there might be some paint scraping involved...
http://www.usni.org/userfiles/file/%20Sept/Selle%20Sept%2008.pdfOf course, even allowing a supercarrier to traverse the canal could be a security nightmare...
Apparently the last U.S. Carrier which was able to traverse the Panama Canal was the WWII era Essex Class, and it's been a couple of decades since those were in service! The last Essex class to be decomissioned was the Lexington, in 1991.
Soooooo, some Chinese company wants to build an entirely new canal, which can handle the largest vessels. They are shooting for a 300 ft width, with a completion date of 2019-2020.
So, we might go from one set of canals to three sets of canals in the next few years...