No secret R* want to bring new cities to GTA Online, it's gonna be a long time though before that happens. Still haven't got heists yet lol.
That picture looks like an updated version of GTA IV. Hmmmmm.
I think they will add Liberty City first as this makes more sense, then whatever city the next game is set in.
Its pre-release screenshot
Liberty City will be added to Gta online they have already spoken about how they want the online world to be huge!