There's no new GPUs coming before CP2077 for his budget, plus he said he needs it now. As for CP2077 performance, it's coming out on X1 & PS4. If you understand what that means you understand a 2070S will have no issue handling it even at 4K, and since they're using TA up the wazoo you can downgrade to 1800p with minimal issues.
The Witcher 3 came out in May 2015,and 10 months before was only Kepler cards,which couldn't handle the tessellation in the game,and CDPR released a slider to help. The GTX980 came out a few months later in late 2014 and obliterated even the GTX780TI:
https://static.techspot.com/articles-info/1006/bench/1080_Ultra.png
https://static.techspot.com/articles-info/1006/bench/1080_High.png
Mere weeks later after the game launched the GTX980TI was launched:
https://static.techspot.com/articles-info/1011/bench/Witcher.png
Witcher 3 released on consoles too, and it didn't run that great. The 8800GTS 320MB and 640MB released a year before Crysis came out and when it was released,we saw the 8800GT and 8800GTS 512MB which were cheaper and faster in the game.
So Nvidia releasing better cards when Cyberpunk 2077 is released makes a lot of sense,as it would be the ideal push for graphics card sales just like The Witcher 3 and Crysis were.
The demos were using a GTX1080TI at 1080p,and you can't make a promise even a RTX2070 Super can run the game at 4K fine,when the top cards of the Witcher 3 era,at ultra and very high settings struggled at 1080p and 1440p. The game was also downgraded graphically.
April 2020 is 10 months away,which will make current Turing 20 months old. Guess how long it was between the launch of the GTX980 and the GTX1080?? 21 months.
I would not upgrade a graphics card for the game until we know for certain how well it will run on current hardware.
Edit!!
If the OP is upgrading now just get the fastest card possible.
TBH,I would have just kept the GTX1660TI until the game is released.