VMware has released the official Windows vCenter Server to vCenter Server Appliance Migration tool. VCSA vSphere 6.0 Update 2m

Check out the great article from William Lam

Also found these great resources on github here

As of writing (16-09-2016) there is still no support to migrate windows vCenter Server 6.0 to VCSA 6.0. For now only Windows vCenter vSphere 5.5 to VCSA 6 is supported

ill update the post if this changes