Cisco will retire its Nexus 6000 switches in mid-2017.
These days Cisco is keener on 100G Ethernet, promising to sell you faster kit for the same price as 40G kit. With that offer in the field, 40G switches start to look a little laggy, so its no surprise Cisco has planned the range's demise.
Cisco's not the kind of company to take something behind the shed with a loaded gun: first it will stop selling the boxes next April, then shipments will stop at the end of July 2017.
Bug fixes will continue until April 2020, but service contract renewals wont be offered as of July 2019.
By April 30, 2022, no support will be available and you'll be on your own if you want to use the switches.
Plenty of time, then, to wean yourself off the devices and onto whatever Cisco decides to sell you next. Or perhaps you'll buy nothing, lobotomise your switches with open-source software defined networking and run it as a white box server until it starts to emit smoke. ®