They are a major force in the Chinese market so maybe it might see some traction there, but otherwise, I still don't see a third mobile OS getting genuine market share.
for normal users they get a improvement in security!
Microkernels by having a reduced risk surface provider better security, less vulnerabilities, and more compartmentalization. Programs simply have less privileges
Harmony OS is closed source, and run by a company in a country that has done some... flexible things with data security... but at least with a microkernel its less likely third parties will violate your security, only second parties here!
I dunno, kinda doubt it.
I don't think most devs will be really thrilled on having to support another platform with a seemingly petty different SDK.
I think that not offering any type of Android compatibility, no matter how limited, will prove to be a mistake