Future AMD AM4 Socket will be µOPGA, and it will have 1331 pins. A LGA solution will be used for Opteron Zen CPUs.
AM4 solution will have the virtue of putting together the plus points of the three actual AMD sockets: AM3+, FM2+ and AM1.
Like AM3+ Socket, AM4 will be able to support 140+ Watt CPUs and APUs. Like FM2+, AM4 will be able to support powerful integrated GPUs. Like AM1, AM4 will allow to realize budget mainboards, as much as high end mainboards: AM4 CPUs and APUs will have an integrated FCH, but a lot of features can be added thanks to external chipsets (more PCI-E lines for multi GPUs cofigurations, M.2 slots, etc).