While my speculations and predictions for their impact on various formats remain optimistic, I believe we havent yet seen the full extent of how many playables Duskmourn will offer
4 card draw
Wan Shi Tong enters with X counters, draws you a ton of cards, and then grows every time an opponent searches their library
For as long as Secret Lair cards remain this difficult to get ahold of, both at and after release, price spikes like Geralfs Messengers are likely to continue.
Additionally, if you can get a lot of characters out fast, and a lot more once Be Prepared is played, you could very likely beat Ruby/Amethyst to the punch
The 10 Worst Cards in MTG Now, we know that youre expecting to see Tibalt, the Fiend Blooded here