As proven with WoW during the Shadowlands exodus, and outlined by Asmongold and Bellular and others, the RP community is likely the last to ever leave your game if there's some gameplay imbalanced or content drought. The community finds its own fun and entertainment though leading stories, personal development, dungeon and campaign encounters that are player designed; it's an endless well of content for people. Form guilds with specific niches, stories, climb the ranks, host your own events, it's all amazing to experience if you ever dip into such an experience.
I myself have been an RP 'main' on WoW since 2012 and on FF since I started. I've tried RP on various MMOs and never found really a tight knit community like WoW, FF and SWTOR have. And these communities will be the ones who will stick with the game the longest, as proven. Investing into emotes, customization, RP addons and player-made environments will bring the game to life even through development phases and content droughts, however I believe such a discussion is best left for after the game has a stable framework for classes, game features and a working 1.0 as all this can be added after there is a solid pve/pvp experience to keep players engaged.
As a suggestion, maybe even at some point do what no MMO did so far. Allow players to palce down NPCs and edit their appearance to look like enemy NPCs, bosses you defeated or even other player models (A bit like Overlord's 'character data' idea) in your personal housing. Some people in SWTOR use this as a way to make dungeon encounters or roleplay nexuses.
I really am looking forward to what the devs will say about this after they sorted out most of their core features.