No. Address the problem directly. Don't ruin Christmas. And don't use it as a threat unless you're joking around with it. Too mean. I don't like any of the ideas which involve even pretending to throw away presents.
To tackle bedtime, you need to work out why he keeps coming downstairs and deal with that. Unable to sleep? Unable to relax? Scared? Lonely? Worried he's missing out on something downstairs? Wanting attention? Finds sleeping boring?
And some ideas to try:
New approach where he's allowed to play quietly in bedroom if not sleepy enough to sleep. Can restrict activities allowed during this time.
Later bedtime and/or changed bedtime routine so he's actually tireder by bedtime.
1 hour period between pjs + teeth and lights out where he can do what he wants, but any coming out after this results in time taken off the free time the next night.
Make out of card some "Night passes" - he can come downstairs ONLY if he has a pass - so he's allowed to come down up to 3 times. Make sure to remind him to save one for an emergency. Some kind of penalty the next day if he comes down without a pass - lost screen time, or earlier bedtime.
Give him a notebook and pencil and tell him to write down any random questions he has to ask you in the morning (Or he can leave them outside his bedroom door for you to pick up when you go to bed)
Pre-empt everything - bottle of water, access to bathroom, ask questions etc, something to read/listen to if he can't sleep.
Audio books or meditation CDs - you can buy these or just find some on Youtube for him to listen to. But he can ONLY listen if he stays in bed and doesn't get up.
Talk to him about how sleeping is good for you, helps you grow, makes morning come faster, and dreaming is fun because you can do anything you like.
Choose a new nightlight or cuddly toy to take to bed if he's feeling anxious or lonely. Even offer to sit with him (if you're happy to) but ONLY if he lies down and doesn't talk at all. It's probably a short lived phase.