Well I think you are more specifically saying you don't see ipad users replacing their tablets with an android tablet? Well yeah that can be an issue, I don't think anyone is arguing that point at all, everyone's needs will be different. My use for my ipad is exactly how Cryates describes it, basically the ipad for me is just a dumb tablet, a really large iphone. But in your case you need specific iOS apps and the pen input, so this won't work for you.
But I do think there is a case for more complex use (ignoring lack of pen input for a second). I'm sure most apps on iOS can be found on Android, and Samsung always works very hard to give its tablet OS much more functionality than typical Android tablets. In some ways the Fold 2 supersedes iOS though, for example wireless Dex sounds really powerful and useful to me.
But do I think the majority of iPad users are going to rush out, sell their iPads and buy a Fold 2? Hell no, this is such a niche market and we are only at the very very beginning stages of a paradigm shift. Whether it's worth the price of a phone AND a tablet is very individual at this point, but IMO in a few years it's going to be a no brainer, but by then Apple will have its own foldable phone on the market.