If Obito Kamui's Minato, Minato can get out Mid-teleportation like it happened the last time, however if Minato doesn't Hiraishin away mid-Kamui he get's in the Kamui dimension with no escape. Yes Hiraishin can't escape Kamui dimension U_U
Now, if Kakashi Kamui's Minato, well If Minato tries to teleport mid-Kamui he'll end up losing his body parts, i.e. the part which Kakashi has focused, as it's been proven by manga itself, there's no escape from Kakashi's Kamui. Best bet in that case would be to get transported into the dimension without resistance. And if Kakashi aims for you head or something well it's a GG U_U