VMware Discontinuation of 3rd Party vSwitch Program for vSphere
3rd party vSwitches including Cisco Nexus 1000V, Cisco VM-FEX, Cisco AVS, HPE 5900v and IBM DVS 5000v.
VMware has release a migration tool which can be found here.
A blog post of what is the strategy forward in terms of virtual switch on vSphere is mentioned here which include virtual Standard Switch (vSS) and virtual Distributed Switch (vDS) and Open Virtual Switch (OVS).
For customer who are on 3rd party virtual switch, you might have to change back with your vendor for your support in future vSphere version. Understand Cisco has mention to their customer that they will continue to support the use of Nexus 1000V.