[breezy25]

I was in the EXACT same position last week when Best Buy gave me a $1,400 store credit after my 7D broke and Geek Squad had to replace it. Expect to take a major hit on value/price of your 5D3 if you buy it now. I was stuck between the 5DS-R (which i have now) and the 5D3 and essentially chose the 5DS-R due to the fact that it won't take a hit in price upon the announcement of the 5D4 due to it's entirely different place in 5D line as a specialized piece of equipment. The 5D3 is a 4-5 year old camera and the 5DS-R came out last fall. The 5D3 took a 30% price drop last fall and is going to take another hit/get discontinued when the 5d4 drops here promptly.
If I end up preferring the 5D4 when it releases, I'll take a minor hit on resale of my 5DS-R compared to the financial hit of the soon-to-be ancient 5D3. This decision will be made based on whether it includes 4K video, better low-light performance, and HOPEFULLY a megapixel count somewhere in the mid 30's!

All of this being said, you should honestly sell all of your current lenses and either opt for a 24-70mm 2.8L for the time being and PREPARE for new lenses with whatever setup you'll have in the next few years. In this case, if budget is a super tight squeeze and you're still wanting a FF body, then I'd recommend looking further at the 6D (or the cropped 7D2) and still building a lens collection before even looking at the 5DS line or the 5D4 because either of these cameras are going to require lenses far sharper than your 70-200mm 4.0L (I currently am getting rid of my 70-200mm 4.0L for this very reason on my 5DS-R).

2 other cool additions to consider with the 5DS line is that (1) they have a function that allows me to change the FF to a 1.3 and 1.6x crop which i have found insanely helpful but is still kinda unnecessary cuz of the fact that I can simply crop in during post production with my 50.6 mp.. .which is INSANE by the way. and (2) i can also change my file sizes from a 50.6mp to a 28mp which is great if file sizes are a concern of yours.

In summary, the 5DS line was just simply "checked off more boxes" in my search for a new body and I'm very happy with my decision.

Hope my rambling provided some decent advice. Take care everyone.