I know you want to jump into the full frame... and I'm looking to get a 5d mkiii within a year.
This is really tough. There is an equal argument for both... and I have ambivalent feelings... I want to say get the 24-70 and the t4i. The t4i will run maybe 650 or so and when you sell it for $500, you won't lose much after a year. I like my 24-105, but I don't love it. Especially compared with my very nice primes (100mm f/2.8L IS Macro).
I've had a few zooms to include the 18-55mm, a 55-250mm, 75-300, 70-300, 70-200 f4L USM and the f2.8L USM. And I've been just disappointed enough in all of them. The 25-105 is good enough in a pinch when I know I need something wider, but indoors, I do need to bounce the flash. It's just not a good enough option.
BUT... I think the 24-70 is still at the plateau of it's highest cost because of production delays and still a decent amount of demand. I think if you waited a year, the cost would probably drop by $200 or 300... but is it worth waiting... probably not.
I know everyone says that there isn't a HUGE difference between the 24-70 and the 24-105, but I like my 24-105, but I love my 100mm f/2.8L prime. I'm not sure how well the 24-70 compares with the best primes, but if it is close, then I'd suggest to go that way.
Well, I'm in a different situation than you, but I've been happy with my 60D, 24-105, 50mm f/1.4, and 100mm. I have about $2300 saved up and I want a 135mm f/2, a 5Dmkii, and a 70-200mm f/2.8L IS mkii. So... not enough to actually get all of what I want.
Basically I'm saying I'm as confused as you are, but I'm happy with my 60D, and I'm hoping to be ECSTATIC with a 5D mkiii. And if I'm not, I'm going to be SO disappointed that I spend 2 grand to maintain the status quo.