In upcoming Additional Content for Three Special Stages, players will be able to acquire weapons from Enker (Rockman World), Punk (Rockman World 3), and Ballade (Rockman World 4) from the GameBoy games. It's unknown if you can use these in the main game, but it's probably likely since I get the same error as I did with Forte trying to use these from a save and askes for Special Stage 1 data. 9 had a single Special Stage, but you could not acquire Fakeman's weapon. Below are some specs of their attacks and what they look like, assuming that's how it's all numbered setted for the SP Stages. I'm sure these stages will be just as exciting as Forte Mode is, not to mention how the new Endless Attack will be in 10.
Mirror Buster (Special Stage 1)
A weapon acquired from defeating Enker. A Shield that converts enemy fire into Mirror shots.
Screw Crusher (Special Stage 2)
A weapon acquired from defeating Punk. A Blade that can be thrown 3 at a time at enemies.
Ballade Cracker (Special Stage 3)
A weapon acquired from defeating Ballade. It'll explode on targets, walls, and can be thrown in any direction.