Maybe, maybe not and it might take quite a while. I have heard that about MSM but I have not tried it. I have a U2 who was about naked and mutilating when she came to me just over a year ago. She is fully feathered now. Another, a female M2 fluctuates with how much feathering she has. With her I don't ever expect to see her fully feathered. If a plucked bird bothers you, other than for the point that they are after all supposed to have feathers, don't adopt the bird. It will drive you nuts and the bird will end up even more unhappy being unloved
With us, "feathers are optional" even though I do all I can to try to help break the cycle of plucking and regrow the feathers.
Good luck whatever you decide.