Also agree. if you are installing vCenter for the first time, you'll probably want to do at least one round of build it up and tear it down, whilst you get everything how you want it and document your build process. 

I would crack on and start doing that with the vCenter that is available now. If U2 comes out in the meantime, do your final build with that version and implement AAD as an identity provider then. Everything else will pretty much be the same.

Even changing from one identity provider to another isn't that big a deal. I'm sure U2 will work just fine, but only you can decide whether to go with U2 off the bat, or wait a while until any potential issues that might or might not arise, are ironed out. 

HTH