Everything is in the title, vSphere 5.5 is dead.
As described here by VMware end of support will be september 19, 2018.
What should you do?
Upgrade to vSphere 6.7 is THE choice i think, if you’re not confident with the last version of vSphere 6.7, you can go to vSphere 6.5.
Not so much to say, the thing to notice is that “Windows Client” is no more available, only web client.
HTML5 client is really handsome, Flex client aka Flash client is also still available, but new features will only be available trough the HTML one, so go directly with this one.
If your vCenter is in 5.5 and hosted on a Windows VM, you can now go to vCSA version, in fact you must go for it, update manager is now packaged on it.
You can directly upgrade the vCenter to 6.5 easily with the embeded tool packaged in the iso of the vCSA.
All informations regarding migration path have been written here :
It’s NOT possible to directly upgrade from vCenter 5.5 to 6.7, you have to perform a jump trough 6.0 or 6.5 again all information here.
On ESXi side, you can perform actions trough update manager, it’s really simple. Before upgrade, check if you’re hardware is compatible with the new version, check the Hardware Compatibility List here.
What’s New in vSphere 6.7?
Maybe, you’re still asking yourself around 6.5 vs 6.7?
A nice whitepaper has been released by VMware with all detailsregarding what’s new in vSphere 6.7.
Feel free to download it here.
You have now all informations needed, if you’re still worried by something feel free to ping here in the comments or on twitter.