Well the only thing we can probably be sure of is that the shards that Rika will end up in from now on will likely be majorly different in terms of the background events and the true perpetrators behind the massacre. It'd be too easy and too boring if this followed the same perps and events because Rika knows all of it already.
Also since Keiichi seems to be in a similar situation as his previous iteration in the shard where they managed to break through June 1983, that he is starting to see memories of previous shards where they failed. The rest of the cast is probably seeing it as well, and this might be the reason why Reina is having those blank stare moments. Since this part is probably similar to the Onikakushi-hen, it seems to be told from Keiichi's POV, so I expect the rest of the arcs to show the other characters dealing with having memories of other shards.
The big question now is what Rika will do when she realizes that her knowledge of everything that happened in the original Higurashi likely no longer applies.