Demand reduces as more team and companies become experienced and learn what it means to work on digital products. Like your EM being concerned about impact of story and and ensuring sprints planning and executions is done well. Product designer taking more ownership into seeing their design built, tested and released and monitor performance. Other functions understanding how org prioritised building of the digital products and making efforts for their case etc...
In a small under 100 org, you may not need PMs, but larger ones does need. PMs per org will see a decrease as every business is trying to be leaner. Anay increase in jobs will only be from more companies being in play.