In that case, a 7D makes sense. But, you'd also probably need a wider sealed lens. Perhaps the 17-40mm or 24-105mm, depending on how wide you like to shoot (check your EXIF from the 15-85mm).

The 7D has the best sealing outside of the 1-series (rank order is 1-series >> 7D > 5DII = 50/60D).