It could well be for iSYL, it was a hugely popular episode, and unresolved as well. But it doesn't matter if that's the one it will be based on. Everyone seems to assume that it might be about Carly thinking now she HAS real feelings for Freddie, that it's something to do with Carly/Freddie. What if it were somehow something Seddie related (which it would be regardless if it's mainly Creddie stuff happening in the episode, or in moments of some of the episode), as in Freddie wanting to know if Sam had feelings for him then already, and that's part of the reason she gave him that 'foreign bacon' analogy? Maybe he's trying to figure out where it all started. And yeah, they could've had that conversation sooner already considering they're supposedly dating in one of the episode arcs, but perhaps they haven't gotten completely deeply into it (as completely deeply as you can get for a show on Nickelodean anyway).
It would make NO SENSE WHATSOEVER to have Carly and Freddie together at this point. There is no character development - in fact, it only regresses back and makes them look bad. There is no logic - so Freddie can only not be 'available' anymore for Carly to want him in that way? There are no issues - Dan has made SAM the one who is IN LOVE with Freddie. Regardless of anything Dan might want to throw at us via his tweets, maybe to stir it up a bit, even if unintentially, at the end of the day it doesn't change the fact that Samantha Puckett loves Freddie Benson, and the boy is damn happy about it. We'll see how they get to that point, and it's gonna be great, and when this 'unresolved' episode revisitation airs, it still won't have change those facts because that would be too unrealistic, too dramatic, too MUCH for a show in this demographic (though I'm sure they don't realize just how many people who watch aren't in their tween/teen demographic at all; said person being one of those people).
I honestly don't care if it'll be based off of iSYL; I actually think that might be a good thing. Perhaps we'll finally get a concrete conclusion to Freddie's whole "And if you still want to be my girlfriend, I'd be really psyched about it" statement. I want it out in the open, I want to know that Freddie doesn't have those feelings towarRAB Carly anymore. And again, I know timewise that it'd likely be nicer to know that before they even go on their date, but as I mentioned, they were probably both too scared/stubborn to talk about it on such a deep level just yet. Whichever episode it is, whatever they're filming in relation to it, I'm not worried. Which almost terrifies me in and of itself because I love these two beyond worRAB, they're one of my ultimate OTPs. But I suppose that speaks to my complete and utter faith in Mr. Dan Schneider. He told us to highlight Freddie's shirt. And we did. "Purple Jerk." A strong pull in one direction. The Seddie direction.