We Are was the only OP in the series that never got repetitive in it's run back in the 90s. Somewhat I've noticed that OP never got old to me when I started watching the series 4 years ago.
But yeah, I liked Crazy Rainbow the 1st four times but after that, it got pretty crappy. Even if it was the animating of the color spreads, it somewhat got VERY tiresome. And to think they played that OP during the most intense of fights in the arc, I mean come on, "Chillin' in da beach", "Usopp sketching drawings in a cliff", "Sanji carrying Nami from a dinosaur", "Luffy and co going shopping", didn't take me long to realize the Op itself got boring and the song was dull, didn't fit the series at all.
As for 5050 doing the new OP, upon listening to their short music clips/vids, they somewhat in "some" way remind me of COLORS, prior this song will be sung by more than two people, unlike Brand New World by D-51 and Crazy Rainbow by Tackey and Tsubasa, both OPs sung by duo artists, I can hope Jungle P will somewhat give me that cheery exciting feeling or "FUCK YEAH! ONE PIECE IS ON!" feeling from We Are as Carter mentioned, but as I said "Hope" and "Speculate" is all we can do, or more specifically, "Speculate" how it'll turn out by judging from 5050s short music clips.