Gyarados...??

It could get new moves when generation 2 comes out.

Wait a week before you pull the trigger

i'd wait but I doubt it would get any better than bite/HP. they won't give gyarados DB back and I highly doubt they'll give him a STAB fast move.

I'm sitting on 2200 candies and am waiting since I already have two good ones.

People keep saying wait on this question and I really don't get why. Bite/Hydropump is awfully good on offense and even if it gets an additional charge move, it's still glass on defense due to typing no matter what move that it gets and it would likely add more chance of getting a less than optimal attacker. If someone already has a Bite/Pump or two I get waiting, but if you don't, things don't always get better, sometimes they get worse....

I mean, you're asking something that nobody could possibly have the answer to...

If you want guesswork then I highly doubt it.

1) They did all the move changes at once early on, which makes me think it was a one time rebalance

2) No Pokemon have more than 3 charge moves, so he's prob not getting a new one of those. Plus his current ones make sense. 1 offensive, 1 defensive, and 1 trash.

3) They took away his 2nd quick move, so chances are it was deliberate to give him 1 quick move like The eeveelutions, Tangela, etc.

If you think about it, it makes sense to only give him 3 moveset possibilities. 400 candy is a big investment to have 6x move combos. 2400 candy for the moveset you wanted is steep. It makes sense for Eevee too, b/c with 3x Pokemon it's 9x combos. If they had made 2 quick moves would have been 18x possibilities every time you hit evolve