Hopefully that will change in 1Q2017 when Xilinx finally releases to production their new Zynq UltraScale+ MPSoC[1]. It has a quad-A53 cluster and a dual-R5 cluster. It is still in early-access so I can't say much more beyond that (we're designing it into a system so I'm constrained by the early-access NDA).

[1] http://www.xilinx.com/products/silicon-devices/soc/zynq-ultr...