I don't think these changes are big revolutions for Genesect, since I'm almost positive that the Choice Scarf sets will still be the most common. They certainly aren't bad though!
Blaze Kick- I see this as being the most used new move. On Physical Genesect, it DOES do more damage to a lot of mons than Flamethrower. This is partly because of the likely chance of Genesect getting an attack boost. A good example is Ferrothorn in the rain: Since they are specially defensive, you dont get a boost, so you are dealing 30.68 - 36.36%. Meanwhile, a boosted Blaze Kick in the rain will deal 57.95 - 69.31%! Be warned though, you can't 2HKO Forretress in the rain with Blaze Kick, you need Flamethrower for that because of the download boost. and you will get hit by Ferrothorn's iron barbs which is annoying, so Flamethrower might still have some merit.
Choice Band will certainly prefer Blaze Kick over Flamethrower though. Forretress is still 2HKOed by that in the rain even without the attack boost, and Ferrothorn now takes a nasty 88.63 - 104.54% in the rain due to the download boost!
ExtremeSpeed- Heh, I had a feeling it was going to get this considering the name of the movie... Anyways, this can be cool on CB Genesect. Now, this isn't going to make CB Genesect a better revenge killer than Scarf obviously, but it sounds like a nice little side job for when you need to kill stuff like weakened Darkrai. That being said, you actually won't usually get an Attack boost vs Darkrai and Mewtwo, since it has equal defense and special defense, meaning you get a Special Attack boost =/. I think ExtremeSpeed has potential on Choice Band, but I don't think it will make it a star. Also, I have to admit, I have a hard time seeing what move it'd replace, since Explosion is great on CB Genesect, Iron Head is actually useful for hitting stuff like Ghost Arceus on the switch neutrally, and Blaze Kick hits steels...
Shift Gear- This is actually the one I'm most skeptical about. While those calcs showed that it can 2HKO a lot of mons in Ubers, several of those mons (such as Dialga) are going to fry you with a fire move. And of course, Groudon will own it. I guess it's a bit of a step up from Rock Polish, but even then, when I used Rock Polish Genesect, I played it like the Choiceless set only missing an extra move (usually U-turn, but sometimes a coverage move if I wanted to do the whole U-turn momentum keeping thing). This is because in my experience, Genesect isn't really a consistent sweeper and its hard to set up despite the Steel typing (and before you say "set it up with Wobbuffet, Wobbuffet has much more dangerous sweepers to set up!). That said, I'll still probably give it a try (maybe with Ice Beam to screw with Groudon), but I can't help but think that Shift Gear doesn't go far enough to help with Genesect's issues as a sweeper due to an iffy physical movepool and somewhat under powered moves. I could be wrong though, I haven't really thought too much about Shift Gear Genesect yet!