Eleague Premier was not during a huge slump. It was literally a month after their huge win at DH Masters Malmö. The analysts will be split when it comes to who will win. I'm gonna guess 5 to G2 4 to C9, but it could also go the other way around.
It wouldn't be an upset if either win. I think if you ask, most people will agree that this is a very even match up, and most will be slightly favored towards C9.
G2 did change their game, but that doesn't matter. At Eleague they were playing with this same less aggressive style that doesn't have as many force buys in rounds.