no one. not a single person (unless I missed it) has mentioned the 24-105mm f/4L lens
are we all forgetting how great this lens is or are we all blinded by the new mark II 24-70 f/2.8

just the fact that the 24-105mm is so affordable now makes it even more attractive and we can't deny that zoom range is extremely helpful and versatile.
with $4,000 to play with you could pick up some fantastic lenses, no need to gun for the brand new $2,000+ lenses
16-35mm f/2.8L II
24-105mm f/4L (or maybe the new 24-70mm f/4 IS USM)
70-200mm f/4L (non IS version)
and I would also consider the 50mm f/1.4 and 85mm f/1.4 lenses by Sigma - they are incredibly good for much less than the Canon versions
and you may end up with money to spare. like I said - no need to gun for the new $2,000+ lenses