Apple Watch 7 is likely to have a version of CGM at launch and is currently undergoing reliability testing as well as stability field trials. This occurs before commercialisation.
Three years ago in 2018, a number of patents were applied for which were finally secured including body odour analysis and absorption spectroscopy to analyse materials in the blood. In-company trials have been on-going for 5 years as well as CIC technology partnerships for the same length of time.
However, those who want to use it as a clinical measurement device should realise that it will be bounded by indicative caveats at the outset as part of an overall fitness suite of apps. Using the feature to accurately determine insulin dosage for those reliant on this to manage their diabetes is not on the agenda and won't be for quite a while, if at all.
My current understanding is the initial positioning and use cases will be more lifestyle - so for example to help stem the tide of the T2 global epidemic by providing users of indicative elevated BG levels so they can potentially invoke their own diet/fitness regime changes.
As other posters have also said, local regulatory approvals will also have to be sought and secured before the app and related features can go live in specific geographies/markets.