I do have a conflicting pro/con of this. The Pro is that it allows new teams (the qualifiers) to come into the LCS rather than the same eight teams that we see in the LCS already. The Con, however, is that a team that doesn't qualify for the next season’s LCS has to win either a qualifying event spot or get Top 5 in Ranked 5’s in order to place in the Promotion series.
Some teams might disband if they feel like they cannot get a high enough rank to place. Take for example, CLG. CLG lost the Playoff match against Vulcun 2-1. If CLG loses to Azure Cats tomorrow night, they might disband because of their recent lack of success and games won. This doesn't necessarily mean that the players on that team will retire, but it will set the players back. The disbanding team members will then have to find a new team and climb that Top 5 ladder or qualify within events just to only get into the LCS Qualifiers or Promotion series.
Even though it depends on the region, I’ll use North America for example, the teams aren't consistent enough. GGU, who placed 2nd in the Spring Playoffs, almost beating TSM 2-3, were the team that got 6th place in the spring season alone. If GGU can beat team Dignitas and team Curse, both 2-1 in the Playoffs, then it really does say something about consistency. As I'm writing this, team Complexity just lost 3-0 to team Quantic, who is a qualifying team. Complexity did so well in the final weeks of the spring season but yet is falling short to a qualifying team that didn't even qualify for the spring Qualifiers.
I know that things change; like Quantic’s roster did with adding Meteos, Balls, and SneakyCastro, which help become a better factor for winning, but for the teams that don't have constant roster changes (CLG and team Dignitas for example), it might hinder that team’s future. If these teams don't improve on what is making them lose matches, they will either disband or will never be seen in the LCS again.
I hope this all makes sense, but I just don't agree with the format Riot is using for successful teams, especially if the region is not consistent. Maybe it might all change next season, for example, TSM. TSM was in 4th place by the end of Week 9. With Dignitas and Curse losing their matches and TSM winning all five of their matches, it brought TSM straight into 1st. One factor why this happened is because of their roster change of replacing Chaox with Wildturtle in Week 6. If TSM becomes consistent because of Wildturtle, then you have one more consistent team within the region.