We’ll have more bosses than ever come Season 2! Blizzard have clarified that the Season 1 boss, Varshan, will be sticking around!
Global Community Development Director Adam Fletcher stated that Varshan will stay when the season ends. Presumably this means both for Eternal and Season 2. However, Fletcher did not address the main question regarding the new Season 2 bosses.
While Fletcher didn’t confirm the Season 2 bosses staying, it’s definitely not ruled out. It makes sense they wouldn’t want to announce them persisting after the season when they’ve just been announced and haven’t even arrived yet.