There is still one big thing that hasn't changed but has been the subject of discussion on whether x86-64 is fundamentally bottlenecking CPU architecture. Variable length instructions means decoder complexity scales quadratically rather than linearly. It's been speculated this is one reason why even the latest x86 architectures stick with relatively narrow decode but Arm CPUs with lower performance levels (e.g. Cortex X1/2) are already 5-wide and Apple is 8-wide.
