Bartman
Welcome to MultiRotorForums.com!!
Actually I'm kind of thinking you should go the other way, keep your T2i, add the ML software to that for aerial and then get the 5D3 for stills and ground based video. I don't believe that ML software will enable your T2i to shoot RAW but it greatly improves the HD performance and makes it comparable to the GH3 and its pretty light weight.
I use the 5D3 for real estate as well and its pretty hard to beat that camera for that application. I thought I might fly it when I got it but its just a work horse of a camera, its become my goto camera and its just making me too much money to risk flying it. I haven't tried the ML RAW upgrade yet, the footage I've seen looks pretty good.
Chuck,
What's funny is that back when I got my T2i (Dec 2010?) they didn't have a ML file for it so I never bothered looking again! Then when I posted this thread I happened to go look to see about the 5D and saw that the T2i is now covered so I'll have to have a look into that. It's a heck of a camera as it's still working great despite a number of spectacular crashes, it must think it's being used as a crash test dummy!
The only problem so far is that the heli to fly the GH4 will be slightly lower power than the 5D and I'm not one for flying huge motors around if I don't have to. I might give it a couple of more weeks to see what's going to happen and then pull the trigger on something.
Thanks for your input.
Bart