It doesn't matter whether or not you ever "go full frame"....
Either the EF-S 17-55/2.8 IS or the EF 24-70/2.8L (orig. or Mk II) will do a great job filling your need. I use the 24-70/2.8 and find it even more useful as a portrait lens on a crop camera, than on full frame. The 17-55 is an excellent alternative at a lower cost, obviously with a somewhat different range of focal lengths.
Both of these are f2.8 zooms, which would normally be my choice over any f4 zoom in this range of focal lengths.
When I know I'm going to be shooting only in good light and want to lighten up my kit (such as when hiking or biking), I use a 28-135 IS that I picked up used for $250. It takes the place of both of my larger zooms: 24-70/2.8 and 70-200/2.8 IS. IQ of the 28-135 is way better than it's pricing would indicate. Plus it's got fast, accurate USM focus, is an EF lens that will work fine on either crop or full frame, is close focusing, and has reasonably effective IS. It's just not as well built or sealed as the L series alternatives... but costs a whole lot less, is smaller and weighs quite a bit less.