Yeah I think the letter is real, I only have 2 questions about it:
1. We don't know to whom it is written (and I personally doubt it's for LMP or Rushka)
2. We don't know when it's written.. could be 20 years ago for all we know. Some people seem to think it has to relatively recent due to the "4th child" reference, but this might only be symbolical. Maybe he just means to say he wants lots of children with this woman, or maybe 'having 4 kids' is something they talked about earlier, it doesn't have to be taken literally. Same goes for the "wife" reference, he may see her as his wife even though they were never officially married.
Bottom line is: we don't have a clue when or why this was written and I doubt we will ever find out

And maybe it's better that way too.
Well, like I said before it should not be a mystery. If we assume that the letter is real we have to take as it is, to start getting some clues.
If we take it as it is, it is only can be applied to LMP imo. I know , not too many ppl will agree with me but that's OK

It fits the situation and the context imo. Like I said before it probably never have been sent to her, because IF it was it would not be on the net.
I believe personally that Michael had his "ups" and "downs" to Lisa. This is how this letter was born maybe imo.
Why it could be applied only to LMP in my opinion? Because they got divorced and Lisa loved him. It is a fact. Then when he felt lonely and nobody was around, he probably was hurting and he wanted somebody around him and his feelings to Lisa got refreshed at one moment. Probably after this, it was the same again because nothing happened as we know.
Or maybe when she started bugging him sending letters, he did not answer back. Michael had a very sensitive soul and mixed feelings about Lisa imo. So it is a normal behavior when you are not sure. Probably when Lisa was trying to contact him it closed his heart again for any contacts while
"his soul was hurt and his mind was confused". Hard to say. Michael was not an easy person. But this is what I think.
About the last line.... well assuming if it was not added I think it fits LMP only because from Shmuley book we know that the only one person he wanted to have children with was Lisa but sadly it did not work out. This marriage in general did not work out but he had some moments I guess when he was trying to catch up his past with Lisa,
probably only in his mind and this is what I personally feel from this letter.
I do not think that the line "i STILL see you as my soulmate, as my wife....." we can take as a symbolic thing. We take it as it is or we can assume that it was added. Regarding to Lisa it fits the context imo.
This is what Lisa said after he passed. Read carefully. I think it gives more clues that the letter could be addressed to her:
Lisa also said this about the marriage when she received news of his death:
Our relationship was not 'a sham' as is being reported in the press. It was an unusual relationship yes, where two unusual people who did not live or know a 'normal life' found a connection, perhaps with some suspect timing on his part. Nonetheless, I do believe he loved me as much as he could love anyone and I loved him very much. As I sit here overwhelmed with sadness, reflection and confusion at what was my biggest failure to date, watching on the news almost play by play The exact scenario I saw happen on August 16th, 1977 happening again right now with Michael (A sight I never wanted to see again) just as he predicted, I am truly, truly gutted. Any ill experience or words I have felt towards him in the past has just died inside of me along with him. He was an amazing person and I am lucky to have gotten as close to him as I did and to have had the many experiences and years that we had together. I desperately hope that he can be relieved from his pain, pressure and turmoil now. He deserves to be free from all of that and I hope he is in a better place or will be. I also hope that anyone else who feels they have failed to help him can be set free because he hopefully finally is. The world is in shock but somehow he knew exactly how his fate would be played out some day more than anyone else knew, and he was right.
Looks like she was upset at him till his death.
According to what Karen F said after MJ passed, he had no secret girlfriend. I know many ppl hate Karen but at this point I would believe her. Yes, he was socializing with fans and such after 2005 but it does not mean anything imo.
I am not LMP fan cos she said so many bad things about him but I am trying to be more realistic and more logical here.
There is always some mystery around Michael but I do not think this letter is the case. Just saying... .