T J McMahon has suggested in a comment at Stand Firm that the release of the ++Rowan's letters suggests a failed attempt to blackmail ++Rowan:
Well, I guess the one positive thing I can say for +Rowan Williams is that he did not succumb to blackmail when someone called or wrote him last week and said something to the effect of : “If you don’t say A and do B, I am going to give a copy of this letter to the press.” ‘Cause I can’t see anything to be gained by either him or Dr. Pitt handing it over to the Times at this point. If Dr. Pitt wanted to damage +Rowan, the time to have released the letter would have been the day after the Lambeth invitations went out, or after the bogus JSC report on the HoB meeting. And certainly, I can’t see +Rowan releasing it himself.
I guess that a blackmailer would need to follow through on the threat to release the letters if the threat failed to get the desired results. That way, the next person threatened will know the blackmailer is serious and will follow through.
If the blackmailer were a Reappraiser, the blackmailer's hope might be to
(a) antagonize the GAFCON crowd into breaking with the Anglican Communion,
(b) permanently damage ++Rowan's relationship with the Pope so ++Rowan is no longer motivated to please the Pope and would then be freed to follow his liberal inclinations regarding same sex blessings and sexually active gay bishops.
If the blackmailer were a Reasserter, the blackmailer's hope in releasing the letters might be to
(a) create a climate demanding ++Rowan resign.
Then again it may just be spite.