So here it is, pictures and all (comic book) guide to upgrade your vCenter to 6.5 based on the today released GA.
Mount the downloaded vCenter iso and navigate to the vcsa-ui-installer and choose your install flavor. Hell yeah! no more client integration plugin! I tested with OSX and Windows.
The OSX gave me an error at the select deployment size, maybe a bug? Did not look at it further, OVF tool was available but might be a patch thing:
So went on with the Windows installer.
Click Upgrade or Migrate from your Windows vCenter. Stage 1 will now start.
Accept the EULA and click next.
Fill in your current VCSA information.
Accept the certificate warning if applicable
Pick a host or vCenter.
Pick a new name for your target appliance.
Choose your size 
And pick a datastore
Input temporary IP settings.
Review your inputs and flip the finish switch..
Press continue and start the upgrade path. Stage 2.
Click next and pre-upgrade checks will be run.
Port 22 needs to be open on your source vCenter. So enable SSH on your vCenter
http://blog.ukotic.net/2015/06/14/enable-ssh-on-vcenter-server-appliance-6-vcsa/
You might get some warning (This is a LAB so no worries) close them:
Choose your data to migrate:
Join the program to support the cause, or not, go next.
Flip the “i have a backup” button and finish off. (If you did not backup then you are a karma basket case)
Go Go GO:
The waiting game beings………
Tick Tock..
Oh Yeah! starting:
Importing data from vCenter 6 Appliance:
All Done!
Log in and test all. Flash be gone, Loving HTML 5.
If all is good then you can delete your old appliance. If not, this is the part where karma hits you in the face when lacking a proper backup:)