The PSO League will probably be around for as long as the PSO website is around. Why? Because it's a good way of getting people to make a deposit while at the same time teaching them to play good poker. If you never made a deposit at
pokerstars you can only advance to High School level which is not bad but in order to advance to the University and Master levels you must have made a deposit at PokerStars anytime in the past.
Is it worth it? If you're serious about playing competitive poker then yes, definitely. The top 300 of the High School level shares a prize pool of $2805 at the end of the month scaled according to position. The top 150 at University level shares a prize pool of $7990 according to position. The top 100 at the Master level shares a prize pool of $15,300 according to position. These prizes are given at the end of every month based on that months League points.
The top prize for High School level is $150. The top prize for Master level is $3000. So, people will obviously want to make a deposit of $10 at least at PokerStars to qualify for the upper levels of the league. Also, once people made a deposit and played something other than free-rolls many of them keep on depositing.
So yeah, it will last a while I think.