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!