Absolutely. I'll even go one further: we won't actually know the exact moment that Level 5 arrives.
Cars with level 4 + remote assistance will be driving people around for a decade or more, phoning home less and less over time until one day someone notes that no car has phoned home for an entire year. Then maybe a car will phone home and the clock will start again. Decades from then, people will shut down the last remote assistance center.
But at that point, nobody will care about declaring Level 5 because we will have been riding around for decades in cars without steering wheels that we don't have to drive.
Cars with level 4 + remote assistance will be driving people around for a decade or more, phoning home less and less over time until one day someone notes that no car has phoned home for an entire year. Then maybe a car will phone home and the clock will start again. Decades from then, people will shut down the last remote assistance center.
But at that point, nobody will care about declaring Level 5 because we will have been riding around for decades in cars without steering wheels that we don't have to drive.