If the game gets popular, it sure as hell will. As little as 350 default movement calls at 10fps half way maxes out a 3.5ghz thread, and since BYOND's single threaded that could impose a big issue for a lot of games.
What in the name of spode are you doing that maxes out a 3.5ghz thread at 3500 movements per second?
I've had 50,000 objects moving per second in my test environments on a 3.6ghz core I7.
http://files.byondhome.com/TheMagicMan/walkrand.jpg
This is 2169 mobs at 10fps doing nothing but walk rand. It hovers around 20% cpu usage.
Anyway, as far as I am aware there is no BYOND game that even has half as many players as this active at once. And if I'm not mistaken, BYOND doesn't handle movement the same way it handles procs being called so it's not really accurate to compare the two.