I wouldn't count on it being a low price in the summer. Summer is when you see almost no discounts at all. The winter and early spring are when the biggest discounts seem to occur. Like I said...I do doubt it will go lower than this in 2013...at least from a reputable dealer. There will be ebay "deals" lower than this. What really counts is, will we see used 6D's in the summer going for $1100 or under? If so, it would be best to either buy used, or else buy a new 5D3, in my opinion (and wait for it to be discounted again...the 5D3 has fallen farther since its introductory price...but used models haven't fallen much at all).
To factor in that the body is $1500 and the lens is $750, is not really correct either. The lens is really being discounted more...as a kit lens they're getting $500 or so for it. Which is why it makes no sense to buy the 24-105 by itself. Just as the 18-55 EFS lens, as part of a kit, is really selling for about $60. By itself it's 2 or 3x that.