Bleach might return, or Gintama.

I'm not sure if you could call One Piece a cash grab since Oda had intended to make One Piece a very long running series. His intentions don't seem bad but I feel like there's too much derail going on in the series so he could do a better job of cutting things out rather than prolonging it. 

Dragon Ball is part of the "Legendary 5" Here's a picture illustrating:

One Piece (the manga) is certainly not a cash grab (at least not to the level that Bleach/Naruto have become), but the filler filled anime certainly is. Instead of just doing seperate seasons, fans get to watch though hours of filler before the manga gets ahead enough.

The series that's in it's final arc and put its anime on hiatus so the manga could finish, costing it much popularity in the process, is a bigger chashgrab than OP?

You'll be surprised but out of the big three it is One Piece that has the least amount of fillers in the anime ... 

The pacing is absolute crap since the studio only animates one chapter of the manga per episode compared to both Naruto/Bleach pulling off a much more reasonable two chapters per episode so that's the main reason why I can't fucking stand watching One Piece ... 

So we are going to ignore the cringe-worthy amount of filler that the Naruto anime had before, not to mention the noticeable drop in quality during and after the Pain arc?

I suppose I can agree there, out of the three One Piece has aged the well in both anime and manga. I still find the anime a bit frustrating and the manga harder to follow than ever, but it isn't on the level of the other two.

Seems like ending will be rushed. Can't see it ending in 5 chapters.

Wait a minute, when did I ever say that One Piece has aged well in both the anime and manga ? If anything it's aged just as poorly as the others ... 

The anime is frustrating for sure and I can agree with you there since it's sooo damn slow. It would be in your best interests to not try and make any sense of One Piece's mediocre plot development. What people really like about One Piece is the sense of adventure rather than it's poor excuse of a plot. 

Personally though I always thought that One Piece has peaked a long time ago at Enies Lobby and I found Marineford to be very underwhelming ... 

Oh, it hasn't aged well, but compared to the other two, I think it has done relatively well. Naruto and Bleach should have ended years ago, while I can see some justification for One Piece still running (some, mind you, not a lot even then). I personally gave up on all 3 around three or four years ago, there comes a point where it's hard to keep up with the weird plot designs the writers pull to try and keep the series alive.