2 trapinch questions

1) Whatever Niantic feels like giving it. Given that Flygon has no real signature moves in the main series and that it doesn't really need better charge moves (aside from outrage, which would be super lame/predictable as the dragon CD move), I'd put money on flygon getting dragon breath from a CD. That's about all that I could see making it better, but even then Flygon would probably run Mud Shot as the superior electric/fire counter move (to which flygon has immunity tier resistance) for PvP purposes. For PvE, nothing is going to make flygon relevant. It lacks the stats.
2) Yes Flygon is usable in Ultra league, but he's nowhere near as good. The presence of so many legendary threats in the pool (such as bolt/beam mewtwo or blizzard kyogre) really puts the kabash on Flygon's usefulness. In great league, most mon's with ice moves are either water or ice type, which means that covering flygons weaknesses isn't overly difficult. In ultra, that pool expands to include psychic types. Ultra league is also ruled by Giratina, who absolutely poops in flygon's cheerios.

TL;DR: I wouldn't put money on flygon getting a CD any time soon which will make it better in PvP, and it's far better in great league than ultra league, but it's still usable in ultra if you really want to give it a shot.

1. Draco Meteor or Outrage would make it strictly better for PvE as a dragon type attacker, though heavily outclassed. As mentioned, Earth Power is in the game master but doesn't have any stats attributed to it. This is where it has the most potential to be good; If it's added as a Dynamic Punch clone it would surpass Rhyperior in ground type DPS while being more fragile.

2. Ultra has Giratina running rampant which kind of kills its chance to shine.

It can do well in ultra as a sort of mini giratina, as well as the ability to counter some of the better giratina counters. Ground does good damage to the glassy Lucario, double weak aggron and MS/EQ can do damage to Steelix after a Giratina's shield broken. It can also spam DC because of the high EPT MS has, however Giratina is strictly the best dragon attacker in the league.

I'd personally hold onto any good ones you get incase we get earth power as a CD move or something. as groundleave a lot to be desired offensively in good moves. It wont out DPS the likes of groudon or likely garchomp, but could be a great budget option if given high powered ground moves.