WWE RAW on Monday did a 1.87 television rating, according to the Pro Wrestling Torch. Because of the Independence Day holiday, it was expected to be among the lowest-rated episodes ever. This is probably the sixth- or the seventh-lowest rating* since beginning of the Monday Night Wars in September 1995.
This individual low rating isn't really cause for alarm in terms of signaling that WWE's popularity is falling. Other indicators of popularity -- live event attendance, merchandise revenue and Google searches (adjusted for all Google use) -- are all stable over the last several years while ratings have declined.
The overall decline in ratings may be attributable to a number of factors surrounding the evolving media environment: WWE being viewable on YouTube and Hulu, USA Network just recently becoming available on Sling, DVR use, the three-hour length of the program fatiguing viewers, etc. Regardless of the reasons, the overall decline of WWE's TV ratings are still concerning in that they will affect future TV rights deals. Money from current TV deals represented 35% of WWE's revenue in 2015: that's more than the WWE Network or any other single segment of their business. The company's largest TV deals are up for renegotiation by 2019.
Barring a real surge in popularity for WWE, its ratings will likely continue to decline as time goes on. It's true the viewership of most programs, especially scripted ones, are declining sharply. Live programming, especially live sports are holding up better. Whether networks still consider live content such as RAW and SmackDown to be as valuable in 2019 as they did during the last TV rights negotiations in 2014, is probably the biggest question for WWE going forward.
*Records of WWE RAW TV ratings collected from the Wrestling Observer Newsletter only go to one decimal place, until 1998 when it began reporting the rating with two decimal places. So the 1.9 on March 3, 1997, could have been rounded from anywhere between a 1.85 and a 1.94. Similar for two 1.8 ratings on September 25, 1995 and October 14, 1996, and the 1.9 rating on September 25, 1995 -- it's unclear whether the July 4, 2016 rating is higher, lower or the same as those ratings. However, if the two 1.8 ratings were only rounded between 1.75 and 1.84, which seems more likely, Monday's rating would be higher than either of those.