After spending some time looking at SQL Server 2012 CTP3, it appears as if Transactional Publication with Updatable Subscriptions will officially be removed in SQL Server 2012. According to Books Online, Microsoft is recommending that users switch to Peer-to-Peer Replication instead. This is a shame considering Peer-to-Peer is an Enterprise-only feature and will cost significantly more than Standard Edition. On the other hand, we will still be able to achieve updatable subscriptions in Standard Edition via Merge Replication or Bidirectional Transactional Replication.
Here are the screenshots comparing the SQL Server 2008 R2 New Publication Wizard with the SQL Denali CTP3 New Publication Wizard: