A lot of people have been saying that it's unfair that Dan has "ignored" and "abandoned" the Creddie story lines (iSD and iSYL) and that he needs to acknowledge those again. While I do agree that these should be revisited more explicitly, at the very least for a sort of final closure, I do think Dan probably feels like he's already started to revisit that storyline and make it clear what happened with Carly and Freddie post iSD and iSYL. I think the answer to their feelings and the beginning of an acknowledgement of the creddie storyline is in iSAFW (I know everyone hates that episode, but Dan really said a lot of important things with it.) These quotes in particular say a lot in regards to Creddie. In fact, I think these were all meant to begin giving closure to Creddie's iSYL and iSD and possibly pave the way for Seddie (not I said begin to give closure. Dan still has work to do there if he wants to make it believable.):
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Adam: "So are you and Freddie, like, a thing?"
Carly: "Me and Freddie?! No...I mean...What!? I'm completely available."
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Adam: "So you and Freddie definitely aren't together."
Carly: "Oh God no."
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Fan: "Carly and Freddie, what are the circumstances surrounding your romantic relationship...?"
Carly: "Freddie and I aren't in a romantic relationship."
Freddie nods in agreement
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Fan: "Anyone who has ever even been to iCarly.com can see that Carly and Freddie are in love."
Freddie: "No we aren't."
Carly: "We really aren't."
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Sam: "I was just messing with you guys when I said Carly and Freddie were in love."
Carly and Freddie nod in agreement.
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Freddie said he and Carly weren't in love and I suppose it's up to you if you believed him, but I did. I think he really didn't feel that way about Carly anymore and hadn't for a while. I think THAT was Dan's way of beggining to revisit the Creddie storylines and letting the audience know where Freddie and Carly stood. No, it wasn't a grandiose revisiting, but I do think it was meant to be a nod to the relationship. I think Dan will revisit Creddie more so during the Seddie arc, but essentially, what I'm saying is that I don't think he completely abandoned it like many are saying. He just relied more on inaction to explain what happened to Creddie (which is lame, but like I said, I think he'll revisit it more during the arc and I feel revisiting it is essential for a realistic development of Seddie).
Also, I think what we were supposed to get from all of this was that the hero worship from iSYL faded and Carly went back to feeling like she always had about Freddie. Just friends. She never felt the need to bring up dating him again because she didn't like him "that way". Hence no blatant revisiting of iSYL. As for Freddie, his crush on Carly, over time, faded.
I could be completely 100% wrong here though. I'm not Dan, so I have no idea what he has planned in the long run, sadly. lol Just my thoughts. :)