freejung - 11:12 pm on Jan 14, 2011 (gmt 0)
I say it will help. Less pages meaning more link juice to be spread upon the pages that stay.
I'm not commenting on whether this will hurt or help overall in the long run, it'll be very interesting to see, and of course there are several components to link juice now, but just in terms of pure PR the math doesn't necessarily work out that way.
Suppose that all of these supporting pages link back either to the homepage or to the main 20 pages or both. Then yeah, by linking to all of those subpages, the main pages are losing juice, but by having links _from_ all of those subpages they're gaining juice back. Also, each page is a source of a small amount of PR just for existing, and with 5K pages that adds up. On the other hand, each link loses juice because of the damping factor, so having all of those links results in some loss.
I don't know eactly what the damping factor or the source value are, but my guess is that the math is balanced so that, all other things being equal, it works out roughly the same as far as the PR of the main pages are concerned.
More than likely, any difference in the ranking of the main pages will be caused more by issues of theming and/or other link-graph-related factors, but not by a significant change in raw PR.