What happens to intrinsic factor exactly at the terminal ileum, where B12 is absorbed?
After reversible attachment of intrinsic factor-cobalamin complex to its ileal surface receptor, an energy-dependent
process prevents removal of the complex from the cell surface by EDTA or acid; cobalamin dissociates
from intrinsic factor and, as suggested by previous
workers, binds to a molecule antigenically similar to
transcobalamin II; and  intrinsic factor is slowly(after some hours)degraded and forms breakdown products that are detectable in ileal extracts.

References 
Textbook of Pathology Page 318

One article
Intrinsic factor mediated absorption of cobalamin

Recent articles-
Physiology of absorption of vitamin b12