I posted this theory somewhere else, but "48 character, 4 cuts (could change)" doesn't necessarily screw K. Rool if he's part of the 48, and the "could change" part is in reference to low priority veterans who could either add to the character count or the number of cuts, depending on how things shake out. Of course, it's just one theory out of many, and ideally, RosalinaX will still be shot down before long.
Actually, it's forty-eight characters (subjected to change) and four cuts, not vice versa.
That being said, the RosalinaX leak being true, doesn't necessarily mean he's out, but it does significantly hurt his chance of getting in. However, two things bothers me about the leak.
One is that we don't know what exactly RosalinaX meant by forty-eight characters and four cuts. Obviously, that is the most likely scenario, but this could mean anything. It could be what you said, it could even lower than that, or it could be a very optimistic scenario where RosalinaX's tipper thinks in slots for Brawl and thinks that forty-eight characters is thirteen more character than Brawl and that we actually have five cuts to deal with (meaning we'd actually get fifty-two characters). There's no true way to verify what the exact scenario is for this game if the RosalinaX leak is true by speculation alone.
Another thing is that if we take it how it most likely is; forty-eight characters and four cuts, that wouldn't take into account that both Mewtwo and a revived retro characters have been hinted at being playable and I have a very hard time seeing either being excluded from this game because of that reason. In a way, having the Sal Romano characters + Mewtwo and a retro characters (both of which have been hinted at) would contradict the RosalinaX leak. If Mewtwo and a revived retro character do show up, it would either mean that the leak is inaccurate (not necessarily a made-up fake) or that RosalinaX meant something entirely different with the part about "forty-eight characters (subjected to change) and four cuts".
There's two opportunities for the RosalinaX leak to be shot down before release:
1. If we see inside drifting return without nerfs.
2. If Sal Romano leaks again and it doesn't match up with the RosalinaX leak.
I'm putting a lot more stock into the Sal Romano leak than the RosalianX leak, so if the Sal Romano leak said something that contradicts the RosalinaX leak, I'm going to believe what Sal Romano's tipper obtained.