Why the canon 17-55 f/2.8 and the Tamron 17-50 f/2.8? I'd be selling one, unless you have a reason to use both that I don't know about (like how many bodies do you have?). (But then, i'm not one to talk, i've got 7 primes and a zoom covering 50-55mm)

I presume you'll sell the Sigma 120-400 when you get the canon 100-400L? There's probably going to be a replacement of the L within a year or two, depends how long you can wait.

I'm contemplating a fisheye too, the Samyang is an interesting one because it's Stereographic (ie you get more definition on the edges), but the sigma 4.5mm is the only circular fisheye for crop, depends what you want (or you could always get both )

Rest of the kit looks good, i'm kinda jealous. 50/1.2 or 85/1.2 would both slot in nicely there...