Since the iPhones are Google Cardboard compatible, you can already use the Daydream, but only in a very limited way, which is the reason why I would advise against buying it with the intention to use it with an iPhone X. The remote is not usable, as far as I could find out from a quick search. And that is actually too big a limitation. The glasses themselves only contain the optics and no electronics, so it doesn't matter which Dayview you use. The newer ones are nicer and a bit more comfortable than these. In the end, the remote is the reason to choose a Dayview in the first place, because with it you can take halfway reasonable control. Still a long way from Oculus Rift or HTC Vive with controllers for both hands.

"Now that Samsung is on board with Daydream, the View's biggest limitation is a lack of iOS support. Apple's high-end iPhone X uses VR-friendly OLED displays, but don't expect to ever use one with a Daydream View. Google supports basic Cardboard apps on iOS, but Bavor says it couldn't optimise the iPhone for Daydream without the low-level system software access it has in Android, and that it would take too much work to re-create the entire Google VR service library for iOS. "It's not in the cards at all for now," he says."

If you have another source that promises full compatibility in the meantime, it would be interesting to post the link here.

Otherwise, perhaps flirt more with the Oculus Rift Go: Oculus Go 32GB + Carrying Case (in action), or the 64GB version Oculus Go 64GB.