Please answers below queries:-
1. Does PCIe Gen4 IP is supported only in Ultrascale+ device family
2. Which Vivado version supports the UltraScale+ device family.
1. Yes PCIe Gen4 IP is supported only in Ultrascale+ divice family
2. Vivado 2015.3 supports Zynq ultrascale+ with Gen4 IP support.
Virtex and kintex Ultrascale+ devices are not yet supported in any vivado versions.