HI There
Well, I've still got my FE lenses - but I don't have a body, because I didn't like either the A7 or the A7r (for different reasons). I'm hoping that an A9 later in the year will address my issues - if not I guess I'll sell the lenses and stick with the M.
To get me back in again they would need to address only two issues:
1. a quieter less clacking shutter - whatever anyone else may say, I needed two to three times the shutter speed on the A7/r when handholding as I do on my Leica M - there isn't any reason why it should be different. EFC and a quieter shutter would do the trick.
2. less shutter lag - it isn't terrible, but it is there, and for me to buy into a whole new system they should be able to deal with this - Fuji, for instance, on the X-T1 seem to have managed to remove it almost completely.
I would also really like to see IBIS - now they have the 'partnership' with Olympus surely this could be managed (it would certainly be worth a little more bulk if that was the penalty). But IBIS isn't a deal breaker, just a real want.
I'm not so much interested in AF on legacy lenses - and to be honest I think the chances of Sony doing it are so remote as to be negligible: why spend money developing something which is likely to impact the sale of their own lenses? It's the reason why they aren't ever going to properly address the corner issues with M lenses - where's the profit?
Like Marc - I loved the A900, and I'd love to see a simplified interface, but I suspect that box ticking rules this out too.