So.... here is my theory on how Seddie or Creddie can happen now after ILY.
Sam said that she would tell everyone that SHE broke Freddie's little heart. So, she would probably tell Carly this and say that she doesn't have feelings for Freddie anymore. This would lead Carly into thinking that if she ever did get together with Freddie that it wouldn't bother Sam. Thus, not ruining the Cam relationship.
I can see there being a dialogue or an episode where Sam and Freddie get into an argument with one another where Sam says or does something that makes Freddie doubt her feelings towards him. This would lead into it being "okay" for him to date Carly again if he ever did. He probably would focus back on the unkept promise that he made with Carly if he believed Sam didn't love him anymore.
Now for Carly -- I think Creddie could happen with her liking or not liking Freddie. Obviously, if she liked Freddie it would lead into her telling Freddie she wants to date him, and Freddie dating her. BUT -- I think the arch showed viewers how desperate Carly is in getting a boyfriend. I could easily see her getting frustrated in not finding anyone, and going back to Freddie. Like, a scene where she is alone and is upset/frustrated over a recent break-up and Freddie asks her if she would like to try again with him again, as they had promised one another. While dating, even if Carly started off not liking Freddie romantically, could lead to Carly falling in love with Freddie, and Dan could then make Creddie endgame. But I won't get my hopes up too high :p
Now, back to Seddie being endgame -- I could see Sam getting upset, and having Freddie and Sam getting into an argument over something where Sam lets her walls down again and admits that she still loves Freddie. Of course, if Carly was dating Freddie just to have a boyfriend, it wouldnt be a big deal if Freddie started to date Sam again. If she does have feelings for Freddie, I think she would be okay with it, and it wouldn't ruin any relationships. Why -- well, I think the audience is well aware how awesome of a friend Carly is. I believe if she found out that Sam still loved Freddie and vice versa that she would ultimately want them to be happy and not end up jealous. :)
Of course, what could happen could lead into Creddie happening if Dan decides to have Creddie endgame. He could easily have Sam start to like someone else while Creddie is happening, and having Freddie choose Carly and having a cute little reinactment of the door scene with Carly and Freddie from iPilot.
Well yea, here is one of my theory's in how it could lead to either Creddie or Seddie as endgame. Thoughts and comments would be appreciated :)