Pokerstars has been the world's biggest poker site for the past many years and these days there isn't any competitors who are even close to having the same amount of traffic in any games. This doesn't mean that Pokerstars can do as they please however, as they have yet to be granted access to the regulated markets in the US, something they have been struggling to do due to their bad standing.
Earlier this week came the break that Pokerstars may need, as Pennsylvania Representative John Payne announced that HB649 has been submitted to the White House. This bill is primarily focused on online poker and includes intrastate player-pools and no mentioning of "bad actors" or similar wordings, which might open the doors for Pokerstars.
Pennsylvania is currently having a massive budget shortfall of an estimated $2 billion, which means that they need as many operators and as much revenue as possible out of this bill, which may the reason why bad actors has not been mentioned, in the hopes that Pokerstars will join.
Should intrastate player pools be approved upon it will also increase the revenue potentials massively, as they might share liquidity with Nevada and Delaware instead of only within the state. This means that operators can expect higher revenue numbers and that the state can expect more money in taxes, which is a win/win for all parties - especially the players who won't have to sit and wait for games.
Pokerstars has yet to make any partnership agreements with a land-based casino in Pennsylvania, as they have done in New Jersey, but it is expected that they will do so in the near future. Caesars seems the best bet for Pokerstars to join forces with, with their new found friendship, but only time will tell if Pennsylvania is actually a large enough market for them.