Unfortunately, it doesn't appear as if WWE is planning to add any more matches to the Extreme Rules PPV. According to Dave Meltzer in the latest Wrestling Observer Newsletter, WWE held creative and production meetings on Wednesday and decided to leave the card as it is.
Why is that unfortunate? Well, there was speculation that The Kabuki Warriors vs. Women's Tag Team Champions The IIconics and Intercontinental Champion Finn Balor vs. Shinsuke Nakamura would be added but WWE is clearly now taking a slow burn approach to those feuds.
There are, of course, ten matches that have been announced and at least one of them will take place on the Kickoff show.
In terms of ticket sales, Extreme Rules has done better than Stomping Grounds but is still expected to be the lowest drawing PPV for Philadelphia in recent memory. Tickets have not sold out and WWE has been offering 2-4-1 deals for the past few weeks.