Do you think any of last week's Pokemon-we-gave-new-moves will get more usage because of these new moves?
Spike Cannon lets Mega Heracross break through Substitutes on Ground-hating Pokemon, which is relevant because Rock Blast is its only Skill Link attack Poison types don't resist. Not great, but it's something. All the other Pokemon are outright lacking Earthquake/Ground coverage in general, though Escavalier is the main one I could see genuinely appreciating it. (Switch in beloved Fire type that Escavalier is obviously going to die to, lose it to Spike Cannon, whoops)
Extreme Speed helps Rapidash, though there's a question as to whether it'll avoid just being an Arcanine knock-off, provides Sharpedo the excellent Fire/Water coverage (In priority form on both, no less!), lets Swellow push past the few things that outspeed it, renders the Latis slightly more godlike than before, and gives Escavalier the ability to function outside of Trick Room. (Though it would probably rather have Aqua Jet so it could effectively finish off
Fire types that switch in, but whatever) Oh and Ninjask has it now, though I'm not sure what competitive use it will have. But at least it's not capable of going faster than the eye can track in
gameplay too!
Tail Slap gives Ambipom excellent Fairy coverage for Skill Link sets, and makes Skill Link sets marginally more appealing. (It doesn't have a lot of 2-5 hit moves normally) For Technician sets it also can gamble on the possibility of a pay-off -or it can run it as its default if it wants Frustration for primary STAB, which is
entirely possible. Oh and Delcatty has it now, and nobody cares.
Which/Do Pokemon gain/lose an advantage from Rock type Take Down, Dark type Thrash, Steel type Razor Wind and Grass type Natural Gift?
Take Down is a bit more niche than I'd thought it might be, because 90 BP/85 Accuracy makes it a very shaky choice over Rock Slide and Stone Edge. Nonetheless, for Altaria, Arcanine, Basculin, Bibarel, Cherrim, Dewgong, Escavalier, Flareon, Furfrou, Garbodor, Girafarig, Leafeon, Linoone, Luxray, Mightyena, Pyroar, Qwilfish, Rapidash, Sawsbuck, Sharpedo, Stantler, Staraptor, and Stoutland it's vaguely conceivable they might appreciate the Rock coverage it provides. Basculin and Altaria are the two big ones that stand out to me as potentially caring -in the case of Altaria, Rock is a way to hit Fire types super effectively even if they're Flying or otherwise immune to Earthquake (ie it lets you murder Charizard, Talonflame, etc) while Scarfed Basculin is a thing that happens and Basculin even has Rock Head.
Thrash I'm honestly not sure how much of an effect it will have. If you want raw power, Frustration is weaker but doesn't lock you in. But Dark is impossible to be immune to and is in fact a really good offensive typing, so possibly what might happen is stuff like Dragon Dance Thrash Tyranitar comes along to punch holes in teams. Not sure.
Natural Gift being Grass type has no real effect because it fails if the user isn't holding a Berry to determine BP and typing.
Razor Wind is an awful, awful move with awful awful distribution (Special move found almost exclusively on Physically oriented Pokemon) and making it Steel is only marginally helpful. There is
one niche use I noticed looking over what learns it though -specifically Noivern
might run a Power Herb Razor Wind set to surprise Fairies. Even then, normally Noivern runs Choice Specs with Switcheroo and so on, and Hidden Power Steel with Choice Specs hits harder than Razor Wind does, so it's
very iffy.