Roughly speaking, they should work as they have before.
Keep in mind, Blue Iris has never been officially ONVIF conformant. Blue Iris claims to support ONVIF but it is unauthorized and untested by ONVIF.
As such, from the perspective of making Dahua and Hikvision work with ONVIF, unless Dahua and Hikvision remove ONVIF (which I don't think they will), it should work with Blue Iris as it does currently.
Sorry I'm not too sure about how licensing and stuff work, but won't it be like Huawei's case with Google Service where they can't get Play Stores onto the phones?
I was assuming that they would need the license from ONVIF to make devices ONVIF compatible. Are they still allow to produce new units with that standard if they are not licensed to do so? Blue Iris uses ONVIF but doesn't produce units that are ONVIF compatible so I'm not sure how it will be legal wise.
I guess worst case if they ever come up with a new standard Blue Iris will just push a software update to grab the new camera feed.
The Google play services are a framework that connects to servers and provides access to all of Google's various offerings.
Onvif is a protocol that is directly implemented on cctv equipment. All it does is provide a set of standards for 2 or more pieces of equipment to communicate, it's not really a service in and of itself.
I'm not sure if onvif even license the standard, but even if they do, it's not really in their interest to stop people using it unless they're forced to.
Hopefully it'll all be resolved when pumpkin Jesus is locked up anyway.