TheOptimizationIdiot - 11:35 pm on Apr 1, 2013 (gmt 0)
Generally afaik IBL is understood to be In-Bound Links, so my interpretation of the post is the speculated shift is from content on-page to In Bound Links to a page, which could (would afaik) include on-site links to a page, but is definitely not limited to on-site links to a page.
From what I know of general use of abbreviations IBL includes any link to a page. So rather than your distinction of a shift in focus between on-site and off-site links, any link (on or off site) is an In Bound Link to that page and that is what's being speculated at as the 'shift' in importance for rankings over the actual content on a given page.
If I'm missing something or misinterpreting, hopefully the OP will give us a more definite interpretation of what they're saying.