Yes ACGME will be the only residency accrediting body.
If you're talking about US MD graduates.... for most students and programs nothing will change. There will be more programs available to apply to but this will mostly affect the minority applying to small highly competitive specialties like surgical subspecialties. The vast majority applying to IM, FM, peds, psych, neuro, gen surgery, obgyn won't be considering these new (formerly AOA accredited) programs. Programs in all specialties that previously didn't consider DOs because they got applications from enough highly qualified US MDs will undoubtedly receive far more applications from DOs but I suspect they will continue to pass them up sight unseen.