there's a survey going around to random player accounts asking for "who would u like to see in SWGOH be made available as a playable character" (not verbatim, just a guildmate sharing his/her experience to us) i believe three of the options were Bossk (a male Trandoshan, BountyHunter faction), MotherTalzin (Nightsisters faction), and Darth Revan (nuff said). So it is a statistical possibility to still have DR in game someday.
p.s. : Darth Nihilus was way too overpowered as well in the lores, but they managed to find him a nice place in SWGOH so , "Let's go Darth Revan cmoooonnnn!"