I think the adapters were a stopgap solution until native lenses are released. I think you have a specialized need that admittedly many of us enthusiast have. As for the A77 or other A mount cameras - it may be a great fit for you if it works accordingly for your needs. I think it's only a matter of time before Sony completely drops the SLT in favor of just making a mirrorless A-mount camera as it just makes more sense to me provided the body is still ergonomic.
I don't think we will see a mirrorless A mount camera for quite some time.
On sensor PDAF was never designed for A Mount glass, correct me if I am wrong though. CDAF is all that works and although accurate, very slow, hence the reason for the SLT mirror or in this case the same applies to both Nikon and Canon have to have a mirror and a separate AF system that has been around forever and all these lenses were all designed for this.
I think the next A Sony A mount camera will still have the SLT in place though maybe a way to swing it up, like MLU with CDAF for those who need that extra 1/3rd stop of light that SLT eats up.
I just sold my A99 and picked up a A77II and I have my A7. Like all of us, frustrating that Sony is slow to release FF FE lenses, has anyone tried the A Mount Zeiss 16-35 with the Sony adaptor? I am sire it will be no where as good as the WATE though and I am not holding my breath for Sony's new WA FE FF Zoom, it will probably be just ok but not great who knows hope I am wrong we will see..