The game this one is based on is called Cyberpunk 2020. Makes sense this one would be called Cyberpunk 2020 as well. Except, we can't call it 2020, since 2020 will happen in 7 years, which is too soon. Back in the 80's, 2020 seemed like a lifetime away.
Now we need to go much further into the future, and since they've made the decision not to retcon (props for that I guess, stick with what you've made, mistakes and all), and go through the third edition and all of that crap, I can see why they'd throw it a few decades after that, to allow for plausibility in the world being "repaired" back to the state it was in 2020. I guess those are some of the reasons why it takes place in '77.
So, since it makes sense it would have a year in it's name just like Cyberpunk 2020, it's obvious name should be Cyberpunk 2077.
As for a sequel... I think it should be Cyberpunks 2077 2.0: Episode II - First Blood part 2D, Die 2 Hard 2 Furious.