I did some thinking on the subject. What we know so far is that the game still remains in prealpha stage and it probably won't be shown publically until it reaches at least an alpha stage (just like The Witcher 3), so in other words all the features will be implemented and working in some way. Based on the demo impressions a lot of features seems already implemented and working fine, like city, AI scripts, crowd simulation, dialogue system, character creator, combat system, physics, driving mechanics and so on, which is a lot and not all of them were polished properly yet, but by alpha standards this is something that should be expected. However in interviews developers were still talking about how they are not sure about certain features or that they are still working on them, so they can't tell how in the end they will turn out, which indicates that for the game to become feature complete and reach alpha stage will take at least another few months of development. That would align nicely with Video Game Awards and it's possible that the name of the file displayed during E3 reveal (gk) really stands for Geoff Keighley, so if the game will be in alpha by then, they might show the gameplay there, especially since Cyberpunk will definitely be nominated as the most anticipated game of the year. In this scenario reaching the alpha version by the end of 2018 will be definitely a good news, but of course Cyberpunk would still need to go through alpha and beta tests, which in case of The Witcher 3 took as a whole something like a year and three months, but seeing how the game is already longer in prealpha then Witcher 3 was, I'm quite sure that alpha and beta tests will also last longer, so I'm betting on 2020 release and probably closer to the middle then beginning of that year.