Your analysis is dead on. There is NO other sign one can take from this, other than the deal has been struck.
I wonder how many people know that Jack Kemp was picked to be the VP in secret meetings in 1995, long before the Iowa straw poll where Gramm and Dole tied?
This fundraising letter will seal the deal IF it raises money. If the Palinites actually donate to the RNC. If it works, she will be their girl. And it is already over. If it doesn't work, expect them to try it with some other and throw her back under the bus.
I predict it will triple whatever goals they had for the letter, at minimum. The jourbalists might want to practice saying “Madam President” and not for Hillary.