The IQ of the EF-S 17-55mm f/2.8 is superior to either the 16-40mm or 24-70mm L's. I know you said you ultimately plan to migrate to FF, but until you do 17-55mm is a much more practical focal range for a crop sensor body. You'll find that on a crop sensor body 24mm is just not wide enough (especially indoors) and that the 40mm is just not long enough (especially for head shots) for all-purpose shooting so you'll be changing lenses all the time, which isn't practical for photojournalist shooting.

BTW, full-frame is not necessarily the best for photojournalism or, especially, sports, which is why the 7D (1.6x crop) and the 1D Mark III (1.3x crop) are so popular with professional sports photographers. They are fast and their file sizes are smaller and easier to transmit to publishers.

Unless you are certain that you are going to go with a full-frame body in the short term future, I would get the best all purpose lens for the body that you currently own. These L lenses simply aren't designed for your current equipment. Don't handicap yourself.