Str82u - 8:56 am on Jan 11, 2013 (gmt 0)
How is your traffic now? If it ain't broke - don't fix it... or just experiment with it.
It will reduce your sites number of pages.
It would increase the size of each page.
How many redirects/missing pages are there going to be?
is the sitemap going to adjust automatically?
You probably have a long list of things like that, those were retorical - no need to answer. If the traffic were really good and the site contiinues to grow then I wouldn't change anything except to maybe try to freshen up code or remove errors in the pages.
EDIT: Sorry to forget - if you do end up with enough 404 errors - YES, it will affect rankings.