They are 2 problems:
1. Today you buy vSphere 6 Lizenz. After that you can downgrade the Lic within your MyVMware portal to get a vSphere 5 Key. So not a big deal!
2. The edition "Enterprise" does not exists anymore. You have to buy E+ but can only use the features from E to get it equal with your existing Hosts. In the last 2 years VMware say that customer have to upgrade to E+ because in a future Version of vSphere you cant upgrade your Lics and have to stay on 6.x as long as its under support. For a long time there was a promo available for upgrade vom E to E+. This 50% promo ends last year
Notes:
- When "Advanced" edition went away VMware lift all customer to Enterprise edition years ago. Maybe DRS went to Standard in the future?
- vSphere 5.5 runs out of support these days and when possible you should consider upgrading to 6.x
Regards,
Joerg