Because of the new changes this season will bring, I am curious if this will lead to the speedruns only competing against season 13 runs with the addition of post and pre season 13 or if it continues to only be post an pre season 11

The initial reasoning for post and pre-season 11 was the level rebalance. This changed runs by the order of multiple hours, vs a few minutes in places. We're discussing the best adjustments to rules to accomodate the season 13 changes but, as seen in heart of fire it will likely be allowed and where necessary rules will be amended, eg sea dogs parkour (sword) and no sword