Pochama and Yannapu (and also Kirikizan vs Enbuoh as another titled, short battle), might be incredibly short and just a way to show of Shizui. I think it's too early to make solid guess on Kotetsu being the new rival.
Yep, it says how Kotetsu is the new rival is in there.it doesn't get much clearer than that.
Sarcasm aside, we don't know why he knows this kid yet. I'm not saying he isn't a new rival for Satoshi, I'm saying that the assumption he is at this current point in time is hasty.