Probably. I tested a Lexar Pro 600X, which is rated at 45MBps average (~60MBps burst) on the 5D3, and recorded ALL-I clips at over 101Mbps. However, even at this high bitrate I found IPB looked better for the same scene (less compression artifacts and noise). In my tests, ALL-I can look sharper out of camera (due to macroblock aliasing), however IPB can be post-sharpened more (less artifacts & noise). You might shoot with both ALL-I and IPB and compare. IPB works fine with inexpensive 20MBps SDHC (max ave. speed for SDHC on the 5D3 is 20MBps) and uses 3x less disk space (however does require a more powerful computer to play back smoothly).
