Upgrading only vCenter from 6.5 to 6.7 without support agreement

Hello,

I have a client who doesn't want to extend service agreement for vSphere and vCenter.

Their current specs are ;

vCenter 6.5 8815520

vSphere: 6.5 8935087

As Flash support on all browsers ends by Dec, 2020, they have to upgrade to 6.7 Update3, but they don't have service agreement.

So I went to my.vmware.com and was able to download 6.7 Update 3 for vCenter. What is the consequence of installing this update for vCenter without service agreement?

Will it be just for them not having technical support if the upgrade encounters any problem?

Also, is it OK, just to upgrade vCenter only, not vSphere? I think it's OK as vCenter 6.7 supports ESXi vSphere 6.0...