Starting with the fall TV season (2013-2014), the Nielsen company will begin counting households that don't watch TV traditionally (i.e. over the air antennas, cable, etc.). This means that the overall average of homes counted will be more (upwards of 1.5 million new homes added). Ratings across the board will drop slightly, due to Nielsen's system measuring the percentage of homes watching specific TV programming in comparison to the amount of TVs being viewed at that time.
So WWE and TNA will see a slight drop in the overall rating, due to the fact that the homes that do not receive Spike TV or the USA Network will be added to the base of potential homes that could be watching their programming.