I know that a few years ago, Indesit merged the Hotpoint and Ariston brands together on the European mainland with the intention of eventually phasing out the Ariston name.
here in Italy -but also in many other euro countries- still there is the double brand Hotpoint-Ariston vs Ariston by itself as it was time ago.
Anyway it's actually Indesit that merged into Ariston-Vittorio Merloni, not the reverse. The odd fact is that "Merloni Elettrodomestici CO" turned its name into "Indesit Company"
My guess is that the "Ariston" name will be kept for air-conditioner, boilers, solar heating equipment and the like with Merloni Termosanitari, while "Hotpoint" will supersede it in the field of home appliances with Indesit Company