I don't think its trajectory needs to change.
For me, personally, the iPad Pro doesn't offer enough to make it a compelling alternative to the Mac. However, clearly people exist who prefer it.
I think Apple has figured out a system by which the Mac and iPadOS can cross-pollinate to some extent, which some people seem to insist means they'll merge in the long run. I don't think so. They just inspire each other.
Now, the pace I'm less happy with. We're eleven years in, so roughly in the equivalent of the System 7.5.x era. At that point, macOS had already grown a ton, and it had some very clear killer apps, such as DTP. I wonder if that's what's missing for the iPad, and I do wonder if, around the time Steve died, there was a decision that they no longer want/need to do excellent first-party apps. (Keep in mind the iPad 2 was introduced with Garage Band. Where's 2021's equivalent of that?) Decent apps like Linea exist, but no must-haves, it seems.
And while I'm happy how much more discoverable they've made multitasking in iPadOS 15, I just can't see how it took the company that brought GUIs to the mainstream about six years to come to the insight of "what if we added a button, and it pops out a menu?".