I personally think the closest thing to Genesect we'll ever get is Choice Scarf Jirachi. Access to similar coverage + fast U-turn - no STAB on it nor Download sucks when compared to Gene though =/.
Albeit not as conventional, scarf Hydreigon
could replace Genesect on some teams - 98 speed is just 1 point short of Gene so he virtually checks the same stuff and he has a few cool resistances to take advantage of.
Hydreigon @ Choice Scarf
Levitate
4 Atk / 252 SpA / 252 Spe
Hasty / Mild
~ Draco Meteor
~ Fire Blast
~ Superpower / Focus Blast / Earth Power / Earthquake
~ U-turn
It's U-turn isn't going to be stronger than Genesect's anytime soon, but it's quick enough to grab a momentum shift. STAB Draco Meteor hurts pretty badly, hydra has nothing to envy Latios in that regard. Fire Blast and SP/FB/EP/EQ deal with steels trying to sponge a meteor. Since we're using a scarf, obv speed is the n1 priority; but if you're not too worried about other hydras or +1 Hax / Scarf Kyurem(B), just boost your special attack.
I also see Scarf Lando rising in usage - 101 speed, U-turn, HP Ice and 2 good abilities to take advantage of. I've tried a scarf special set and was pretty content with the results.
Landorus @ Choice Scarf
Sheer Force
4 Atk / 252 SpA / 252 Spe
Naive
~ Earth Power
~ U-turn
~ Hidden Power Ice
~ Focus Blast / Psychic
Its main benefit over the physical scarf is that it arguably functions outside of sandstorm better due to not being reliant on it to power its STAB. It is a little weaker than physical Landorus otherwise, but the boosted special moves come in handy against some of the dragons in OU.
Special Lando definetely has a better time revenging +1 dragons (except chomp lol); which was one of scarf Gene's most important jobs.