Are we going to run into some kind of fundamental limit at around 500 million transistors per square millimeter or how long this can go on? Not complaining, jus

Are we going to run into some kind of fundamental limit at around 500 million transistors per square millimeter or how long this can go on? Not complaining, just genuinely wondering. The M1 Ultra is at 130 million transistors per square millimeter, and the processor in my first computer had 7000 per square millimeter, and that machine could already run Doom and Windows 95.