Don't buy any current Alpha mount lenses, as the next year will see revisions to the existing designs, of that I am sure. The SSM lenses are going to continue as they are, SAM lenses the same, but anything currently with a screw drive focus will be replaced with a motor. I also suspect there will be less emphasis on all-round kit zooms, and more focus on fast lenses, prime lenses, and special purposes lenses for Alpha.
The Alpha 7XX (750?) will have 1080i video and exactly the same sensor as the NEX5/3. It will not have Quick View live view, but an update to MF Focus Check Live View incorporating Contrast Detect focusing exactly as in the NEX5. The optical viewfinder will be comparable to the A700, and it will have SSS. What's missing is the new lens. The A7XX prototypes were shown with a CZ 16-80mm. This lens is completely unsuited to video, screw drive, noisy focus and a rather non-linear zoom cam.
So my guess is that at photokina 2010, we will see a new 16-80mm with SSM and improved overall build quality - or possibly a revised 16-105mm instead. I think they will go for the 16-80mm and keeping the CZ name. This lens will also be totally compatible with the NEX and Alpha adaptor.
Two other lenses which must be revised are the 11-18mm (replaced with a 10-24mm SAM) and the 18-250mm (replaced with an 18-270mm SAM OSS). They will also replace the Sony 75-300mm with an SSM OSS 70-300mm f/4-5.6 if they stick with Tamron. And I think they will ad the 60mm f/2 Tamron macro to the Sony range as a SAM lens.
The Alpha 7XX will also have 7fps, will almost certainly offer sweep panorama, wide range 3-shot HDR and almost all the key functions of the NEX including auto magnification of manual live view.
This is all prediction based on what I've seen and heard, but nothing here has been told to me directly. I just have an idea of the three-pronged attack Sony is going to make on several markets at once at photokina. they plan to dominate the pocketable social camera market, the enthusiast SLR market, and the high end camcorder market. They will do this with a simultaneous launch of products across marketing divisions.
Also, I think they are about to replace the current digital photo frames with something entirely new. I will place a bet on battery-power compatible, HDMI+USB2, touch screen, monitor mountable, card storage and maybe large SSD equipped 7 inch 'photo frame' which will also be a media player, a video monitor, an image storage device, a raw file converter, a personal 3D viewer, iPad, PSP, eBook reader, netbook (no keyboard, on-screen) and the lot.
Otherwise, they would not be giving away their 7 inch photo frames with NEX orders to dealers, and would not have given away the 8 incher to the press (mine's going on eBay, I have no use for it and the press trip left me £230 out of pocket).