Yes, the popcorn buckets are still refillable.
here's something to consider, even though I had the old cups, I still bought a new freestyle cup. Depending on how much ur family drinks, it may be worth it. Hint: fill up freestyle cup and immediately pour it into an old cup and repeat in 10 minutes. You can do the math and see if it works out for you.
Also, if you are planning to get the new dining plan, you can add the freestyle cup for only $6. If you are there for more than 1day, recharging the chip for$5.99 is definitely worth it, I know it was for me.