Demilich is the most pushed card in the entire Forgotten Realms set. It will go into Mono-Blue and Izzet decks across all competitive formats and make an impact in all of them.
Its main selling point is the potential zero mana cost and recursive ability that allows it to come back from the graveyard. That is a big deal and everyone will want to play it.
It is being compared to Arclight Phoenix, but Demilich is simply better in many regards, so it can and probably will grow in price in the next few months.