I will re-emphasize what Jensen said.

Do NOT proforma yet !!!!!   It is too early, this is the first release, there WILL be updates to fix errors.  Hell, it's actually the second release as the first one was "recalled" within 24 hours.

IF you have a client that you just must start working on 2019 (say, projections?), proforma just that one.  And be prepared to do it over when software is eventually ready for prime time.