They're taking out a large chunk of general wellness apps. Apps like Fitbit, LoseIt, etc, will be rendered significantly less useful with Apple now controlling the experience for the majority of commonly captured health data (calories, sleep, nutrition, etc). Wearable and other health companies will have to find a way to differentiate their app offerings by including features well outside the scope of Health and HealthKit (think Strava and RunKeeper). Apple is also going after the PHR space, specifically Microsoft's HealthVault. The PHR space has historically struggled to catch on (e.g. Google Health), but I suspect both Google and Microsoft's products were ahead of their time. Although I have concerns about whether PHRs are actually useful, Apple with its marketshare might finally make them mainstream. I can see them extending their new Family Sharing features to family PHR management.
However, I'm struggling to think of how Apple may be able to crack the barriers to data access on the provider/EHR side, if they aim to.