Re: When to start upgrading cameras?
 

I wouldn't necessarily get all one camera. As a multi-shooter, I wish we had stuck with two 70Ds for the autofocus and reach, and two 5d Mark ii's for the full frame and low light ability.

If I upgraded right now, I'd consider two GH4s and two Sonys, for instance, though I also prefer to wait for the next group of cameras that will have a few improvements. Mostly I'd consider what I'd really want, see if there is a single camera that can do it (answer: nope), and consider the best combination of cameras that would. For instance:

I want 4K (for cropping, so it doesn't have to be all cameras), focus tracking like the 70D, full frame, low light performance, and a reasonable work flow.

Re: When to start upgrading cameras?
 

I just made it up ... would be happy to place a bet of £10 that they will bring out a camera like that though!

Re: When to start upgrading cameras?
 

Willing to make that £1000? :D

Ah well, Sony might surprise us, they spit out more camera's then all other competitors combined.