More to come on our afternoon news, about the next AM4 Socket and Summit Ridge. The AM4 Socket will be 40 x 40 mm, like Fm2+ Socket, and the mounting hole pitches seem to be 54mm and 90mm (measured between the center of the holes, of course).
About Summit Ridge, the first revision of this CPU seems to support just DDR4-2400 MHz, and DRR4-2933 MHz when overclocked. These are conservative values, so we can image that AMD has used a standard IMC designed by Synopsys in order to save some money (See AMD-Synopsys agreement) during the design phase. Due to low DDR4 bandwidth, we will probably see Zen APUs with HBM On Package.