I am in the same situation.
Do not file until you know when the new german law takes effect. Once the new german law is published in the Bundesgesetzblatt (has not happened), it will take effect 3 months later. Thus, most likely not before June 1st or July 1st.
In some USCIS field offices, interviews are scheduled within 2 months (with same day oath ceremony).
Also, I believe the new fee ($760) includes biometrics. The old fee was $640 plus $85 for biometrics (which you won't get back even when not needed). So hardly much more..
Good luck.