To me, the "fold" would have to be absolute top-tier, markedly better than anything currently available. More durable for one.
And really, I don't like mini-size tablets, nor do I like Max/Plus size phones. I think to meet my needs, it would have to be a "dual-hinge" folder like the Huawei Mate XT that in "phone" mode is the size of a non-Plus iPhone, but unfolded is not-mini iPad size. And has *FULL* iPad functionality. Now that iPadOS has major improvements over iOS, I don't just want iPhoneOS-but-bigger-screen. When unfolded, I want the full iPadOS experience. (Even if it's only "base iPad" not "iPad Pro" level.)
I'd be willing to pay the premium of (iPhone price + iPad Pro price + a little more) for it. But I think there is zero chance of Apple releasing such a device this year alongside the iPhone 17. And the first generation or two will likely not be something I'd be willing to take a gamble on. So not this upgrade cycle, but next time.
I usually upgrade my phone every 3-5 years. Currently using a 13 Pro, so this year is an upgrade year. And my iPad is getting really long in the tooth - a 10.5" Pro that is now stuck on iPadOS 17. I really don't want to upgrade both in the same year, though, since I hang on to iPads longer. Next year I'll likely upgrade the iPad, and if by some miracle Apple releases an "iPhone 18 Fold" that meets all my needs? I might just upgrade my phone two years in a row and ditch the iPad.