I don't think it would be feasible to release volumes the same month as their japanese release date. Viz has slowed down One Piece with the past few volumes, so I doubt they're making an effort to get closer anyway. The release window was about 9 months after the Japanese date for a while, but has gone back to about 12 months with the extra month delay for Volumes 73, 74, and 75.
Has Viz discontinued the Viz Big line? I wasn't a huge fan of how unwieldy they could be, but there's no denying the significant difference in paper quality. The larger format and color pages are a huge advantage as well.
It's just a shame Viz doesn't print their standard volumes on acid free paper. Viz Sig titles like 20th Century Boys, Pluto, etc. hold up extremely well. Just picked up the first volume of Master Keaton last week. I wish all Viz series were printed in such high quality. All my One Piece volumes are starting to yellow with a noticeable gradient on the pages themselves. Wouldn't care if it was just the edges.
It's a big curious Viz hasn't done any kind of special edition for Fullmetal Alchemist, Naruto, or Bakuman, some of their more successful completed series.
The 3-in-1 omnibus volumes are really a step down from the individual volumes. Are the larger print / format volumes not selling well?
I think I've asked this before, but I don't know if anyone has any additional information.