This one’s tough! Lately Apple’s focus has been more towards readying the software and hardware support for AR (Augmented Reality). Whilst that’s important for them, it’s not so relevant for utility apps like Monzo, and I don’t believe in using a technology for the sake of new and shiny.
I’d personally love to spend more time on some of the older technologies that don’t make the headlines: things like VoiceOver support, haptic feedback, rich push notifications, etc. The combination of these sorts of technologies lead to a much richer, more magical experience than any “big bang” from Apple 