Yes, you can. You can have multiple of these in at the same time. I have personally used 4 of these at a time with no problems. If you are not using too many buttons for player 3 and 4, you might even be able to squeeze it all in with 3 encoders.
The only pitfall you could run into is that if you unplug and plug these back in while playing, it can change around the order of the players, which happens with most USB joystick devices. Under normal cabinet use, you would be leaving them plugged in all the time have no problems.
I just wanted to point it out since I have had a person use these for 2 player cabinets, with plug in and out add on controls for players 3 and 4. He was popping in and out during use, and the USB orders screwed up when doing so. It took tweaking to get the right encoders aligned with the right USB ID#'s so that he plug in player 3 and 4 without it affecting the order of player 1 and 2.