While no significant new additions have been made to the deck, Gruul Valakut, the Molten Pinnacle has reappeared on the Modern scene in a big way recently. It's not the fastest deck in Modern, though the consistency and inevitability that it offers are the envy of many Modern decks. And for games when you need to be fast, well, there's Through the Breach.
A suspended Search for Tomorrow on turn one followed by any two mana accelerant on turn two leads to a turn three Through the Breach, and if everything goes according to plan that means attacking with a 6/6 Primeval Titan along with two Titan triggers. I'm no math scientist, but I've been told that this is easily lethal with a pair of Valakuts, and this sequence is what allows the deck to be a competitor even against the most busted decks in the format. As such, Through the Breach is among the most important cards for the strategy.
Through the Breach has been ticking up in value as of late, and should this deck continue to be a force in Modern you can expect further growth from this Champions of Kamigawa rare. As an arcane spell, it's a difficult one to reprint. That said, there is some real risk to this investment. Modern Masters 2017 was just announced, and Through the Breach is certainly an eligible candidate for reprint. I don't know that we'll see arcane as a theme again as that would be quite boring, but having an odd arcane spell in a set like Modern Masters wouldn't be all that surprising. I expect some more growth in the short term, and should this card be confirmed to not be in MM17, the price could get all kinds of crazy.