Two weeks ago I predicted Ugin, the Spirit Dragon to hit $35-50 in the event that Green Ramp and Esper control remained Standard metagame forces. Those decks have continued to put up results, and Ugin has seen significant gains this week.
Ugin still has room to grow, but the window for Standard relevance on Fate Reforged cards is closing. Ugin will continue to have Modern and casual demand for years, but expect a dip when the card rotates out of Standard. This strikes me as the type of card that you'll want to sell in the short term and buy back later.