Okay here are my 2 cents.
Camera like 5D3 will won't work with with your main "workhorse" EF-S 17-85mm because it only supports EF lenses. Plus your macro 60mm f/2.8 won't work with that camera either. And pictures you take with your 70-300 won't look that good because that lens is weak around the edges and that's exactly what full frame body like 5D3 will exploit. So I wouldn't recommend shelling out 3.5 grand for a DSLR body that makes half of your lenses useless.
For landscape and architecture you want a wide angle lens. Because you have a crop body, if you get something like 24-70 f/2.8, it won't be that wide at those 24mm on the wide end. Yes, it will be ridiculously better quality than your current 17-85 but it actually gives you less focus distance to play with, especially at wide end. And I don't know what some will say but personally when shooting landscapes I found out that every little "mm" at the wide end matters for me. Because the alternative is, you won't be able to fit what you want into the frame.
85mm f/1.2 is pretty much a portrait lens. It has slow focus, and on your crop sensor it will have too narrow of FoV for you to shoot anything with it. So just "no" on this one.
My vote goes for the 70-200 f/2.8L II ONLY if you sell your current 70-300. Yes, you do lose 100mm worth of focal length but I personally think that extra 100mm at tele end isn't as much as for example losing 7mm at the wide end if you get 24-70 to replace your 17-85. I think this is a more acceptable trade-off. And I would recommend selling the 70-300 lens because I don't see you ever coming back to it once you get 70-200, even with 100mm less of focal length. I could go on and on about this lens but you probably already know that it's the best 70-200 in the world right now. You really have to try it to see what people are on about.
In the end, between the choices you provided, I'd opt out for 70-200 IF you sell your 70-300, otherwise you may just get 24-70 because quality-wise its TONS better than your 17-85. The only downside of that is a significant loss of wide angle, which is what you need for landscapes/architecture on your crop sensor, and the fact that version II of this lens will come out in July.
Have you considered 16-35 f/2.8L or 17-40 f/4 L?
I wanted to know If I should buy a new camera or a new Lens here are my choices I have a 600d with 70-300mm f4-5.6 & 50mm f1.4 & 17-85mm f4-5.6 & 60mm f2.8 and I was wondering should I invest in a new camera like the 5d mark iii or invest in a L lens like the 70-200mm 2.8L ii or 24-70mm f2.8L or 85mm f1.2 L.Thank you 
