Not in most cases. There are some motherboards I've heard of where a x4 slot will operate at x1 if another x1 slot is used or if an integrated device (USB 3.0 or SATA controller) is used, but I haven't heard of any boards doing what you're talking about. However, that does not mean they aren't out there somewhere. It depends entirely on the motherboard designers.
The big thing is that there are a certain number of PCIe lanes and controllers on a CPU and some more on the south bridge. With Haswell processors and the Z87 chipset, that is 16 lanes with 3 controller and 8 lanes with 8 controllers, respectively. So, the motherboard maker could run 3 slots that operate at x8, x4, and x4 from the CPU and run two USB 3.0 controllers, two SATA 6Gb controllers, and 1-4 slots in various configurations from the Z87 chip.