I mostly shoot indoor sports and events with a 70-200 f2.8L II. Last year, I made the jump from a 7D to a 5D3 primarily for the high ISO advantage. But, I found other improvements. Color depth was greatly improved, my images are sharper, and I can get smaller DOF with full frame.
My biggest concern was losing the extra reach of the crop body. But, I've found that my 70-200 is sharper on the 5D3, so sharp, I'd rather crop a 5D3 image than use the 7D -- at least with high ISO indoor shots. I think you will find that your 24-105 and your 70-300 will be far better lenses on the 6D than your 7D.
Renting a 6D is a good idea. Take some test shots with the same lens on both bodies to see if cropping the 6D image will make up for the "extra reach" of the 7D. Granted, there will be less pixel density, but I think you will find a sharper image.
The 7D has a better focus system than the 6D. If action is your primary subject, this may be an issue. If not, the 6D is a great option. My advice is not to wait for the 7DII. Either go 6D or wait until you can afford a 5D3. Don't overlook the Canon refurb store.