In the process of the Activision Blizzard merger some decisions have been made that will anger a fair few gamers. Sierra and Vivendi games currently in development have either been migrated into the Activision stable of titles or put on hold while final details are decided.
Games that will be kept are Prototype, Spryo, Crash Bandicoot, Ice Age and one unannounced title. Titles that have not been taken over to the Activision brand are Ghostbusters, 50 Cent Blood in the Sand, Brutal Legend and others. This means that the games will either be published by someone else or close production.
Who will take over these games? At this point in time all we know is that it doesn’t look like it will be Activision, I doubt that they will be be canned completely but as to wether they will still be published under Sierra or if a third party picks them up remains to be seen.