To be honest, the only real change I see actually happening is a huge rise in Crobat usage in OU, possibly even pushing him up to the cutoff. He's always been one of the more used UU/BL pokemon in OU, but his big problem was that he previously had no real way to deal with the huge amount of steel types in OU (Heatwave notwithstanding) and was too easy to force out. Now that he has a way of instantly knocking off 50% of his counters' health, he seems much more appealing. Not to mention his combination of incredible speed, reasonable bulk, good typing, and instant recovery move means that he can keep coming back in and firing off Super Fangs, U-turning out to cause a little more damage, and occasionally recovering off SR damage with Roost. It seems to me like the sheer utility of Super Fang / U-Turn / Roost / (Brave Bird/Taunt) @ leftovers is easily worth a team slot.
As for the addition of Super Fang to Walrein, while it certainly makes Walrein and Hail teams in general much more dangerous, I don't think it is going to have the same effect on Walrein usage as it will on Crobat's usage. Walrein requires a serious amount of support, and in general, the average player does not want to bother with that. I'm not denying that there are some deadly Hail teams out there, but there's a reason why they are not that common.