API Update for Popup?

Has anyone managed to get an updated version so that the API meets the minimum requirement for the ICU Locales?

I have a client who is still running Apex Classes with API Version 43. Their Sandbox is due an update now and their Production org is mid June (as is similar timeframe for all), but I'm concerned that having checked there isn't an update available at the moment and the impact this may have on the current use.

Appreciate an update if anyone has one.