The "rumored" 4th installment discussion, is based on the
"Rockman Boss Character Contest",
that already has a decided winner.Something everyone should remember, first and foremost, the Rockman franchise was (and still is) aimed for children.
That's why they focused on making the games appeal to them, being the fact that the series were cartoon style games, no blood or gore, with only mild violence. When the core fans of the series gets older, it's obvious that any newer versions of the franchise (EXE and Shooting Star) gets the big boot while trying to pull in new fans to Rockman in general.
Complaints isn't just for Rockman alone, it's pretty much every game or media out there. Everyone gets nit-picky because their favorite company doesn't make their favorite games or whatever. People have to understand that it's very difficult to make something that appeals to everyone and not lose a lot of money in the process.
When a side-scrolling game in the Rockman franchise comes out, or a new Rockman DASH, a big fear would be if the game would meet the core fans' expectations at all, or if they will nit-pick about every single detail over and over again until a sequel comes out that meets their expectations. The complaints will repeat themselves over and over again and it's not fun to hear them, especially not if the company hears them.
Because Rockman 9 was pretty much the best games to come out in like ever (and one of my personal favorites), Capcom don't want to make mistakes on this opportunity to create a sequel to something else, and make it as amazing as Rockman 9 was. These fine-tunings and observations and analysis from Rockman fans and inside-developers in the company takes time. Just wait. A new Rockman game as great as Rockman 9 (but for X and DASH series) will come out when there's less nagging about it and when the moment is right. ^^