It depends on the publisher. For third parties they absolutely should support the old gen for at least a year. There are a ton of people who wait to upgrade. It makes no sense not to keep giving them new games.
For first parties it depends. M$ owes Xbox One owners for the poor support they gave the console during it's run, and the XboX only launched a couple of years ago. Their users deserve more than they've gotten so far.
Sony on the other hand supported the PS4 extremely well, and are giving it a great swan song with TLOU2 and Ghost of Sushima. As far as I'm concerned they can do whatever they want. PS4 owners should be happy with what theyve got, and have something to look forward to when they do upgrade.
I was initially not gonna post on this thread since this topic has been argued to death on this site for the last couple of months, but this take called my attention.
Ubisoft, EA, Capcom, Take Two, etc., have ZERO moral obligation to support X1 and PS4 owners. Why? because they were not the ones who sold those people a console.
The only ones with a moral obligation here are MS and Sony; and I for one, find it hugely disrespectful to drop the support of a console even before the next one is released. I mean, by holiday 2021 there will be around 85m PS4 owners who will have one and half year without any game from the company that sold them the console; and by holiday 2022 there will be around 60m PS4 owners who will have TWO AND HALF years without any game from the company that sold them the console.
How anyone who is not planning to buy a console at launch finds this acceptable is beyond me.