Another caveat with the Cortex-A715 is that at lower watts, the Cortex-A715 is still not quite as good as the Cortex-A78, which is important since I imagine Nintendo still wants to have handheld mode run at <15 W, with the performance still being good, and with at the very least acceptable battery life.ARM processors have actually been progressing nicely. You could replace the A78C cores with A715s. This would break Switch 1 backwards compat for what ARM advertises as a whopping 10% increase in performance. You could use A710s instead. This would keep BC, and ARM advertises the same 10% performance increase, but benchmarks suggest the opposite with an actual drop in performance.
I want to mention to the people hoping for TSMC's N3E process node to be used that TSMC's N3E process node isn't a panacea since the SRAM area for TSMC's N3E process node is exactly the same as the SRAM area for TSMC's N5 process node family (including TSMC's 4N process node). And considering SoCs are designed with 70% SRAM and 30% logic in mind, that means that any cost savings are going to be very miniscule in the best case scenario. (Also keep in mind that TSMC's numbers are assuming that chips are designed with 50% logic, 30% SRAM, and 20% analog, which is obviously not applicable to all chips.)