Avengers 4 is already shot, script is done and i doubt they'd scramble for some reshoots just to write out one character in a believable way.
Disney simply panicked and given how this has blown up in their face they didn't want to look weak and go back on their decision. If they had kept their cool, let Gunn make public amends and issue some bullshit generic PR statement (and maybe spin it to actually get some positive PR as reformers of the formerly wicked) nothing would have happened.
People are hypocrites in general.. the louder they yell the quieter they are when nobody is watching and their doing the exact same thing they went up in arms. So Disney wouldn't have lost out at all, Guardians would have been on track productionwise and they could have added a few hundred million to their accounts.
Now it's a big gamble... Gunn was central to the surprising success and i don't believe they can catch the same style again. I don't think the actor's hearts are in it anymore. They will show up of course, no one in Hollywood wants a black mark on his record and a reputation to be difficult to work with but i don't think they'll bring their A game.
So a huge clusterfuck and everybody lost just because Disney fell for some online trolls.