@gerasimos usually, “reaching hardware limit” is not something well known in advance, you plan for what you need, you buy what you need, you use what you need, because buying more than what you need is just a waste of money, PCB space, and even battery life, so choosing a microcontroller is a balanced act, and “provisioning for later” is a very, very hard task especially talking after 3 years, and important company restructuration (Suunto’s last 3 years where not easy, and definitely not the ideal space to think about the possible future updates size when the company was being sold, restructured, etc…).
Also, its pretty hard to compare with competitors, because, yes, they are doing roughly the same stuff , but hardware µcontroller choices are by the dozen, and even inside each lineup, you have a lot of combination of cpu power, ROM, RAM, features.
For example, take the STM32 H7 line :
https://www.st.com/en/microcontrollers-microprocessors/stm32h7-series.html
its just, a single manufacturer, a single chip line from the STM32 range of products, and yet the flash storage range from 620kb to 2MB, and even the processing power varies from a single core at 200Mhz to a dual core at 400Mhz, inside the same “STM32H7” brand, in total there are 12 combinations !
Once the updates start taking more space, you make do with what you have free, until you can’t do it easily, then you have to take time and man-power to optimize, find code that can take less space, do tricks with off-chip storage, etc., but its not easy