This is my take on the Jeskai Ascendancy combo deck, post-Treasure/Dig! I still think this strategy is viable, and I've gotten turn 3, and more consistently, turn 4 wins with this deck with rough playtesting. Obviously, I need to put it to the test of the current format, but I think just the pure explosiveness of being able to combo so quickly and having such a great variety of winning strategies in one deck makes this seem like a very fun deck to play.
Ok. So, the main card of the deck is Jeskai Ascendancy. A great opening hand usually will include one or two lands, Jeskai Ascendancy or Glittering Wish, one or two mana guys, like Birds or Noble, and the rest being "fuel" cards, or the cantrips of the deck, such as Serum Visions or Gitaxian Probe. If your hand doesn't have a Jeskai/Wish AND any mana guys, it's a safe bet to mulligan, unless you want to take the risk on bricking to finding the pieces. Basically, you set up the combo by playing a turn 1 Bird or Noble, turn 2 Sylvan Caryatid or other Noble/Birds, then by turn 3 or 4, Wishing for an Ascendancy or playing one from your hand. Once that card hits the table, you're off to the races! It's always a great idea to make sure you play the Ascendancy on a turn where you have at least one blue mana or a Gitaxian Probe ready to play, as these will untap your creatures on cast. Once your creatures untap, you tap them for the appropriate mana for the next cantrip/fuel card, and as that card is cast, it untaps you creatures and lets you draw/discard, helping to filter the deck, and your creatures get +1/+1, too! You repeat the process, making sure to tap for as much mana with your creatures as you can so that you get full value on each spell cast, until you either have enough attack power to win in combat, or you use a Glittering Wish you find to get Flesh//Blood, which deals direct damage to your opponent equal to a creature's power. I added Biovisionary/Mirrorweave as a fun alternative way of winning, as I want the ability to, for a tier 1 example, make a Collected Chord player who has the infinite life combo active to have 100000000000 life, and still lose to a non-damaging combo, which can be surprisingly relevant. Feel free to comment and let me know what you think!