The best chips TODAY use chiplets. Check out Epyc, Ponte Vecchio, all high end GPUs and ML accelerators using HBM memory. A chiplet is generally defined as a chip/die with custom interfaces for in package communication.
Also the amount of heat in a given area is rising. We need to spread it out or find some really innovative ways of dumping the heat.
I suspect as time goes on, prices per transistor will become absurdly cheap but you'll need to do things like have redundant hardware running half the time to get rid of the heat.