Qualcomm uses off-the-shelf Arm Cortex-A series cores. Arm has promised between 15-25% CAGR for next generation high end cores [0]. The A13 has ~35% better fp perf and ~50% better int perf than the Qualcomm’s latest flagship, the Snapdragon 865, which uses Arm Cortex-A77 cores [1].

So assuming best case scenario for Arm perf growth and Apple remaining completely stagnant, Qualcomm would catch up in 2 years.

More realistically though, the A14 is rumored to be quite the upgrade. At least more significant a change than the A13. And Arm won’t have a very competitive design until they release their Matterhorn core 2 generations from now, where they’re rumored to finally scale up the physical size.

[0]: https://www.anandtech.com/show/13226/arm-unveils-client-cpu-...

[1]: https://www.anandtech.com/show/15603/the-samsung-galaxy-s20-...