You see this all over the world. One camp wants 'new hardware/software' (NH) with features, another camp wants 'new features' (NF) on existing hardware/software. Every single company that innovates for a living goes through this.
You could argue that Inno has done a good job of both over the years, perhaps possibly weighed a bit more at new worlds rather than new features on old worlds (debatable).
The question is, why do you want a new world. Is it for the existing features of the game? Or is it for new features? If the latter, then you have to ask what new features will the new world have that one of the old ones don't have. If the former, again, you can get that in an existing world. BUT, it's always about customer retention balanced with customer satisfaction, balanced against features that always mess with the first two things.
So, how's this for a suggestion? Introduce something COMPLETELY new to an existing world. But something that doesn't directly affect existing users. Let's just pick something oddball, like a new character class. So in this example, let's say we get a new class called Religious. Only NEW players or restarts can be in the Religious Class. They can't duel, can't battle, but can work, and for arguments sake, say they can go to fort fights to bless people or something. Give them the ability to rise up in rank, and give them the ability to, dunno, increase the luck of the woshippers in that town, whatever, but make it appealing.
To summarize, if we want to retain interest in the game for older players and retain newer players, give them new features but on older hardware (ie existing worlds).