I would wait, at any time Niantic might want to impress investors and rerelease some legendaries. If you need to stash some rare candy, go ahead and put a few dozen into lugia though. I went 4/15 against Lugia but I got really lucky and got a great last one. I have mine at ES/SA right now 3152, has some purpose but definitely not essential. They also might have an easy trading system one day--there are people that would be nice about it
80% Lugia worth powering up?
I waa rather inactive during the legendary bird period, so I don't have Articuno and Moltres (all of both ran away) and my best Lugia is only 80% IV (most Lugias ran away too).
However its IVs are 14/10/12 (A/D/S), and it has DT/FS. The high ATK and low DEF is what makes me want to power it up despite not being a wonder.
I'm still deciding on what to do with it, of these 3 options:
1: Use a fast TM in case ES becomes legacy, and keep it as it is, while waiting for Lugia to possibly come back
2: Use a fast TM and power it up to L30
3: Don't do anything with it, and wait for Lugia to possibly come back
Answers
For what it's worth, I have a Lugia with the exact stats as yours, and I powered it up to 30 with no regrets. Mine has DT/SA, and I use it almost daily to take down Dragonites. I also have a 91% with ES/SA that I also took to 30 but I honestly use it less frequently. DT is really good against dragons.
I love my Lugias.