I just click on the total drama wikipedia and it merged TDAS and TDPI and i don't understand why, i know some articles said 26 episodes where ordered for a 5th season but that was most likely a typo or it was misunderstood as such since no mayor person at fresh TV said TDPI was part two of season five.
Unless the show calls it's self season five part 2 over season six or someone who works on the show confirmes i will not count it as canon.
So that's just my opinion on that matter, and on top of that Wikipedia page just look ugly with the two pages merged like that.
Take a look: Wikipedia (season 5)
Update: i was wrong it seems staff from the tv show creaters did say season five was made in two parts to tell the truth season six sounds better to be over season five part 2.