I think Kevin had confirmed (about a week ago?) in another thread that the weekly challenges we just got are going to reset when Season One starts.

What I did was reroll most of my weekly challenges (since the reroll counter will also be reset, hence there's no reason not to use up the current ones) until I had several challenges that were the same-- in fact, the same as one I'd let roll over untouched from last week's challenges, namely the public dungeon group event in Wrothgar. I ended up with 3 of those, plus 2 for looting treasure chests, and 1 node-harvesting one.

Then I did the Wrothgar public dungeon group event 6 times (took about 30 minutes), which completed those 3 challenges.

I looted 10 treasure chests using some treasure maps, which completed those 2 challenges.

And I used a stack of surveys to complete that challenge.

Rerolls will not carry over to the next Tome, so feel free to use them up because you're going to lose them. Challenges will clear out and go away, so you'll start the new Tome with five challenges (and a short week before you get five more) and five rerolls. If you had 2K unspent Tome Points, then those will carry over to the new Tome, but any points in excess of 2K will be used by the autoclaimer (depending on what remains to be purchased in your Tome) or convered to gold at 10g per point until you're at or below 2K Tome Points for the carry-over. Could potentially be both if you have that many Tome Points and that many unpurchased collectibles.