I can very well imagine Runner mini-expansions to add new people into the mix, kind of like what Sentinels of the Multiverse does. FFG’s proven they can do it before, with the AGoT board game scenario mini-expansions, so I expect that those are a distinct possibility of the game sells well enough.
Which I think it probably would, actually, despite the mixed initial reception. The previous two games were released before Netrunner really exploded the popularity of the setting, and that alone should account for a good chunk of sales.