Lol, did not even noticed.
But it does seem the PageRank update is on its way, but did not ended up yet as http://www.phpbb-seo.com/sitemaps.html
does not have a PR yet (and should).
Would be for sure a pity to end up with 2 on the index and 4 for at least some topics, but we have gone through some major moves in the Backlinks (from 86 to 1500 several times this past week) I still have good hopes it won't stabilize as is. A multi data center PageRank check
shows us that the update is still not done, many DCs are showing a different PageRank.
The PageRank transmission is of course made easier by the mod rewritten URLs.
Looking up a bit more, it appears that many topic do end up with an updated PageRank of 4, but not all, like if the update process was going one right now, because some older but active topic do not have PageRank.
Anyway, these PageRank 4 for topics means Users backlinks will soon be gold [/EDIT]