1. Its named SnS which means Support and Subscription. Its the later one which gives you the right to upgrade the software and receiving new versions and updates for free
2. You can always go for a renewal of your support contracts. If it make sence it depends on the number of years..... if you need a renewal for more than 3-4 years it is maybe cheaper to buy new licenses with new support contracts
3. vSphere 6 needs different lic keys than 5.0
But.. have you checked when your SnS runs out and if vSphere 6.0 was already GA? If so you have the right to upgrade your licences to 6.0 by using your MyVMware portal and choose the "Upgrade" Option in the upper left dropdown action menu.
Regards,
Joerg
