Basically that is what I am thinking.
Leave the landing page http://docs.joomla.org/Upgrading_and_Migrating_Joomla
alone with all the current text intact so that a person landing there knows easily info about each version. The links in each paragraph should be changed to something like this
Updating and Migrating Joomla 1.0 Versions
Updating and Migrating Joomla 1.5 Versions
Updating Joomla 1.6 Versions
Updating Joomla 1.7 Versions
The landing page would be where links like on http://www.joomla.org/download.html
point to. This gives one page that everything official links to for the updating/migrating of Joomla versions. Lock it if desired.
Each link of the landing pages sections goes to a sub-page where the topic is broken down into various sub topics which would be links to some of the existing pages and probably to some new pages. Each sub-page has a link that goes back to the main landing page. say, under a page section named "Recommended next steps" Here we would suggest further work in upgrading their installation and place their landing on the next logical progression.
The linked to or new pages on the sub-pages would lead back to the sub page at their conclusion so that the next linked page may be read if desired. In this fashion proper space can be given to a particular section without making an overly long and boring update/migrate page for the particular topic.
Landing page section
subtopic a ( only if absolutely needed)
subtopic b etc.
Placing a bunch of links to other upgrade/migration pages on upgrade/migration pages as a continuation tends to confuse noobs (especially if they suddenly walk into a link forest) and may make additional maintenance headaches down the road. By linking back to where you came from (can be next section (#) in order if desired) it is easy to see where to go next without getting lost and there are less maintenance headaches with link upkeep.
One section to add to the landing page would be a short generic (not version specific) points to consider paragraph "Before Updating/Migrating" to a new version. Same format as above and would only contain generic info such as back up your data, check compatibility/availability of extensions used, useful tools, etc. between existing site and new version. Specific requirements for a version would be handled within the specific update/migrate page(s) This avoids the repetition within each update/migration section of common info.
**Not sure if the sub-pages should be actual /subpages or just regular pages acting as sub pages.