There is no U3 that I am aware of. We are a paid customer with subscription.
I am currently running vsphere 6.0.0 U2a (VMware-VIMSetup-all-6.0.0-4637290.iso)
With ESXI (VMware-ESXi-6.0.0-Update2-3620759-HPE-600.9.6.5.7-Dec2016.iso) THIS BUILD IS HP SPECIFIC, so its a little behind.
I believe they jumped right into 6.5
Regards,
Wally