IVE feels like a group that is already reaching a certain level of emotional long term attachment to their fans and the industry at large the same way Twice has. It's that same rare quality that has allowed Twice to do world tours long after their prime. I could see IVE going the same path when they are past their prime.
As long as Wonyoung and Yujin are willing that is. They may not want to do the idol thing for that long and want to explore other oppurtunities. This is one advantage Twice has is that they never let anyone become bigger than the group as a whole.
I don't know if I'm explaining this very well. It's just when I watch them performing in concerts I get a strong feeling that their fans are insanely dedicated to them and won't drop them for any other group especially new groups. This will allow them to stay active as long as they want to.
I guess I'm just trying to say there are only a few girl groups a generation that really become something special and IVE is definitely one of them.