No More Heroes 4 could happen, though series creator Suda51 says that fans would have to be really loud about it to get one.
While No More Heroes 3 was meant to be the last entry in the series, Suda51 hasn't necessarily ruled out another game somewhere down the road, though it sounds like it would be quite a long road if it ever did happen. The director recently spoke with GNN about the most recent game, asking if it's possible we'll see Travis Touchdown once more.
"Yes, that’s right, Heroes No More 3 is Travis’ last battle,” Suda said (translations via VGC). "Nobody could say what’s going to happen 10 years from now, and I can’t say either. If there’s a big fan outcry, Travis might be back. Just like Tom Cruise came back as Maverick."
Essentially, fans shouldn't get their hopes up too much, at least any time soon, but Suda clearly doesn't want to solidly say no to another game. As well as touching on this unlikely follow-up, Suda also said he'd like to see a collection of the three main No More Heroes games, but did note that will be up to the game's publisher Marvelous.
No More Heroes 3 launched last year on Nintendo Switch, with VG247's review of the game giving it four out of five stars saying, "Everyone’s going in expecting madcap mayhem, and there’s often no one more stony-faced than someone sitting with their arms folded waiting to laugh. But if nothing else, Grasshopper Manufacture’s latest knows how to make you crack a smile."
Microsoft Windows Store, PlayStation, and Xbox versions of the game were also announced earlier in the year, with a later confirmation that they would arrive October 14. Though the Steam version of the game is arriving a few days earlier on October 11.