If you are going FF just because you want to upgade for upgrading sake then I would advise you to wait for the A7xx

Going FF is changing format already. Apart from the need to get FF lenses, there are these things to consider:

1. The DOF changes. It gets narrower for the same aperture. If f4 can do in APS-C you will need at least a f5.6 or f6.3 when using FF. That means shooting much slower than you normally do.

2. Telephoto no longer gives you that much reach. 200mm will seem short initially for you if you have gotten used to APS-C. So if you are a fan of telephoto range then you need a 300mm to get the same view as a 200mm on an APS-C. If you always use a 70-200mm f2.8 at the 200mm range at f2.8 you are going to feel the pain!

3. The megapixel paradox - Sony only offers 24MP for their FF and that means an increase in all pic sizes. Your current CF cards suddenly becomes low capacity and your PC may feel the load when doing PP. If worse comes to worst, you may need to upgrade your PC too! That's also a cost to upgrade.

4. Fast shooting costs you more - If you're used to the 5fps on A700 or worse the 7fps of the A550 then your only option is the A900 which offers 5fps. The A850 will not satisfy you with its puny 3fps. I don't normally do burst so it's not a problem for me. The A900 is significantly more costly

You are already using a Zeiss lens (16-80). Can you be content with normal lenses when you shift to FF? A 24-70mm will not cover the same range because of the loss of the tele effect on FF. The Zeiss FF lenses costs a bomb. To get an approx of the 16-80 you will need the 24-70mm AND at least an 85mm if not a 135mm. The cheaper option is to get a Sigma 24-70mm f2.8 and maybe the Samyang 85mm but you lose the Zeiss color and crazy contrast and the Samyang is manual focus. Of course you gain bright aperture.

I'm not trying to discourage anyone from moving to FF but it's not a decision to make lightly. Look at me. I have only 2 lenses and they are both old Minolta lenses. Can't afford new lenses. I have another 24-85mm f3.5-f4.5 standard zoom which I borrowed from a friend and that's also an old minolta lens.

The IQ of the A900/A850 is not that much different from the A700 you are using now. Only thing is that it has a higher megapixel count for printing big.

Think about it.