As things stand right now, there is a very good chance that WWE SmackDown could move back to Thursday nights when it moves to MyNetworkTV in September. A number of media outlets that have reported on the move have noted that the reason that MyNetworkTV did not call it Friday Night SmackDown in their press release is because it could be moved to another night.
SmackDown was moved to Friday nights back in September 2005 by UPN (before the WB/CW merger) as WWE did not have a say in the decision. It will be interesting to see if the show moves nights because I was told that was one of WWE’s top priorities in negotiating a new deal for the show.
In terms of popularity in the United States, Thursday nights are the most watched nights on television while Friday nights are one of the least watched nights on television. However SmackDown’s move to Friday nights did not have a significant impact on the ratings.