my preorders:
4 Captain Lannery Storm ($6/set)
Ramps you to 6 mana on turn 4 while pressuring your opponent's life total. If there's gonna be a Big Red deck in the format, this is going to enable it. Absolute worst-case scenario is a 3/2 haste for 2R. Blatantly constructed playable card.
4 Wakening Sun's Avatar ($7.50/set somehow)
Obvious inclusion in dino ramp decks, which will be everywhere even if they aren't competitive. Should not be as cheap as it is considering that mythics are rarer than before.
12 Jace's Sentinel ($1/set)
I know this looks dumb, but remember when Tezzeret's Simulacrum hit like five dollars because of some weird brew that never went anywhere? This is a better card overall, and actually contributes to what 3 mana Jace is trying to accomplish. Someone's gonna try it.
keeping an eye on:
Treasure Map ($7.50/set)
Strong, and will be played in EDH literally forever. Unfortunately, it's slow, Abrade exists, and the upcoming Standard format looks like it'll skew aggressive. It's also not the kind of card that'll get expensive in the short-term; even if it sees competitive play, it's not a 4-of in the decks that'd play it, and casual prices won't spike until it rotates out. Looking to buy in at $1.
Admiral Beckett Brass ($10/set)
The second ability on this card feels like a punchline. Like, if you're actually getting in with three pumped pirates, the hell are you going to steal that will impact the game at all?
Like, I know that doesn't matter, because it's a 3-color pirate lord commander and will be in demand forever. I just hate this card. It's already probably at its floor and Kirblar was right to buy in at the current price, but I'll try to pick up some cheap trade copies instead.
Rowdy Crew ($12/set)
Mythic cantripping creature with low chance of being a 4 mana 5/5. No casual player will ever want this card, and I have no buy-in price for this. I just know that if a deck wants a cantrip like this, it wants four copies. Keeping in my cart during the first GP.
Search for Azcanta ($16/set)
Half of a Sultai ascendancy for 2 mana: good
Threshold, ramp + impulse on a stick: what
Same issue as Treasure Map. Blatantly powerful card, but it's legendary, and probably not a 4-of. Will keep a few in my cart because I want to play with it.
Honorable mention to every other flip card that isn't named Dowsing Dagger. All of the artifacts will be powerful EDH staples forever except Dowsing Dagger, the colored spells have the potential for Standard play, and they should all be purchased when they're in the $1 range. Except Dowsing Dagger.