One consequence of the overrun of the sequence is that the session_id does not fit into an SQL integer type anymore. This can result in cascading changes, when the session_id is used for attributed values stored with type integer in the DB.
One example is the bookmark packages (still at use at OpenACS.org), which uses (negative) session_ids to identify non-registered users. See [1] for a fix of this, which changes the type from integer to bigint.
-gn
PS: http://cvs.openacs.org/changelog/OpenACS?cs=MAIN%3Agustafn%3A20160126084356
