I have quit learning hindi in the past, but had started learning it sometimes. But now I don't think I will ever try to learn it again. I don't think it's useful for me, even if I watch a moderate amount of Bollywood movies.
I also tried to learn Greenlandic once, but since it has so few speakers, it wouldn't be useful. It's a shame because I would love to speak a native American language but due to colonialism there's not one that I could learn that has enough speakers to be useful to me.
I'm currently debating myself for dropping German and Portuguese. Technically I'm still learning these languages but I haven't actually learned them in a long time, except for some flashcards. Since I already know three other Germanic languages, Dutch, English and Danish, I feel my level of German wouldn't drop that much if I decide to stop learning. And since I'm in Germany at least a couple times of the year, I have some natural practice moments.
Portuguese used to be very useful for me since I was in Portugal a lot, but now I don't think that Portugal interests me more than other romance countries. Brazil interests me more, so I've switched to Brazilian Portuguese, but I'm also learning Arabic and Chinese and a little Russian so it's hard to combine. And I get less exposure to Brazil and I still am more interested in the Middle East, former Soviet Union and China.
And what about you guys?