Freely swapping has been a fundamental part of the game since launch, and they even encouraged it more in OW2 with allowing some ulti charge to be kept - which even if they’ve nerfed they’re obviously not keen to back away from completely. So I think you’re very wrong if you think it’s going to get restricted. Losing ulti charge is the natural limiting factor on swaps, and its actually often quite amusing to watch someone constantly trying to find a hero that will work as a counter to a team and in the process completely lose that other key part of the game - the power of ultimates.
So yeah, good luck with your wish I guess. But I don’t see it. Especially as it has the potential to annoy a lot of long term players who like the freedom to switch and would likely get frustrated and stop playing (less money for blizz, longer queue times for those that stick around)