Too many people here are writing sentinels off completely.
Imo, sentinels have yet to demonstrate their peek potential. They've only played two games so far like g2 and have had a very lackluster performance. In the loud game for instance their synergy with their utility was very off (understandable considering the complexity of the comp and the time theyve had with it) but they were still able to demonstrate that their form was intact with clutch potential and hero plays that won them the series. Narrate so far has had a slow start to the season likely because of the role swaps and breach pivot. However, he had been one of the most consistent players in emea last year despite kc doing not much of anything past kickoff, so I'm confident his form will return with more runs on the agent.
G2's synergy has been nearly perfect since the start of kickoff, However. they have not been tested much in disadvantage situations because of the space, flanks and timings leaf has been allowed to take in the last 2 games on chamber. Their chamber pick will be anti'd as well. Considering their success so far g2 will likely opt to improve their weaker maps and might not be willing to adapt their comps and strats much further on their chamber pick maps (their strongest) which may give an opportunity for sen to counter them on their pick.
Map wise both Sen and g2 don't seem to like playing haven and fracture. They share a lot of maps in the current pool.
Sen likely still prefer split/pearl,lotus,bind abyss in that order.
G2 will likely prefer to play abyss,pearl,bind/split,lotus in that order.
Possible map pick/bans
G2 ban haven
Sen ban Abyss
G2 pick fracture
Sen pick split/pearl
G2 ban lotus
Sen ban bind
Remaining split/pearl
In this scenario, g2 will either stick with their double senti comp on pearl or cook up something new to prevent being anti'd. And sen might come with a new comp on split considering their struggles on the map so far with the solo yoru entry.
If Sen improve on their synergy from last time, get a good map pick/ban and start off hot they definitely can beat g2.
P.s. no game is more than a 70/30 between similarly skilled players just because of how momentum based this game is.