That's a paradox--how can you switch swords without dropping it, unless you're supposed to let it ride out?
In which case that makes little to no sense.

Anyone know what the new challenges are? I can tell on Crota that you can't drop the Sword and it has to be a different person.

Well, deathsinger seems to be a straight up race by the looks of the record book. < 2 minutes.

From what I've seen.

Deathsinger challenge is fairly straight forward. kill ALL of the ads, then kill a swordbearer, then kill the deathsinger with the sword

Crota, is that no one can use the sword more than once

Just in case anyone is trying this blind tonight I'll wrap this in a spoiler tag. According to Reddit:

The Deathsinger Challenge seems to be kill all enemies quickly (Yellow bars and thrall), and Ir Yut will 'scream in fear'. At that point more enemies spawn outside (including some Ogres), you need to kill all of them - also very quickly - before a Sword Bearer appears. Kill the Sword Bearer and use his sword to kill Ir Yut to finish the Challenge. The difficulty is that her liturgy is still on a timer - you need to get all the enemies down and have the sword in hand fast enough to drop her before she finishes her song.

The Crota Challenge seems to be simpler. After someone picks up the Sword Bearer's sword, they're not allowed to drop it (by switching weapons) - they need to wait for it to disappear from their grasp. The second requirement is that no one can pick up the sword twice, so effectively you need a different Guardian to run up and sword-slam Crota for each cycle where you're downing him. Don't forget he auto-enranges at low health - might want to save your best sword guy for that run.

Good luck Guardians. Wish I was free tonight (but I'll see some of you tomorrow)!