It's interesting to note that when the locks in the Canal were constructed, the largest ships in the world at that time were 1/10th the size of the locks. People were upset that such large (read expensive) locks were being built. After all, the locks are 1000 feet long, by 110 feet wide. These things were gargantuan back then.
If there really is expansion in the works, that's a good thing I suppose. Although it will be a long and expensive project.
The Navy is currently constructing the next class of aircraft carrier, CVN 21 (although hull numbers will begin with CVN 78). These ships will be 1092 feet long, by 134 feet wide, and displace over 100,000 tons. Too large to fit into the locks currently. The first ship of this class (hull number CVN 78) is to be placed into service for fiscal year 2015. I would assume that the Panama Canal locks enlargement will be completed by then, but we'll see.
Isn't it cool that something built so long ago is projected to continue serving so long into the future?