We know that after the big bang from LIBOR to SOFR, LIBOR will eventually disappear.
This brings up one question that I do not have a clue to answer: How to evaluate derivative in a consistent manner that is comparable before/after the transition?
For example, we are currently using LIBOR zero curve to evaluate equity option's implied volatility. If we switch to SOFR curve with a spread/gap comparing to the LIBOR curve, we would know for sure that our evaluated implied volatility is not comparable to the old LIBOR one.
The zero curve spread between LIBOR and SOFR can be evaluated when both of them exist. But when LIBOR is eventually retired, we cannot know the gap anymore.
How do we deal with this dilemma?