Note that this hasn't changed in a long time. Meaning: they'll never get to release them in bulk.
"If a username you would like is being used by an account that seems inactive, you should consider selecting an available variation for your use on Twitter. In general, adding numbers, underscores, or abbreviations can help you come up with a great available username."
Every time I read this page, (I checked it a few times because @timothee is taken but has never been used) I'm amused by the "if blah blah…, we offer no solution. But here's a 'solution' that we'll tell you is even better even though it's clearly not."