Really, there were so many things that happens to SC that it's hard to say that any one thing delayed it more than another.
I will agree that further releases of any series on the PSP are extraordinarily unlikely, though. If 3rd is coming, there's still a remote possibility, I suppose, if Sony wants to play ball, but Crossbell would be a PC-only enterprise barring a PS4 Kai version, which would be sweet as hell but hasn't been remotely announced. And I really, really, would not get your hopes up for any possible 3rd release on the PSP.
And just to put it completely to bed right now: this tease is as much a surprise to me as anyone. At least as of the last time I spoke to XSEED about it, a collaboration on further projects in the "Trails backlog" seemed extraordinarily unlikely due to a variety of factors. I don't mind admitting publicly that I find this somewhat disappointing, as I really rather like Trails to Zero and Trails to Azure, and not only did I still enjoy working on Trails in the Sky SC and the Sky cast (yes, despite everything you may have read), but I've always heard a lot of praise from Trails veterans for "my" Kevin (I did do very nearly all his dialogue in Sky SC) and I'd certainly like to contribute to the continuation of his story. That said, XSEED is Falcom's primary English-language localization and publishing partner, the decision for who they bring on to work on the Trails franchise is theirs alone, and I respect their judgment. They want to do right by those games, and their fans, and if they feel CF isn't a part of that, then... I'm saddened, but so be it.
So: Carpe Fulgur isn't working on Sky 3rd or any other Trails-related project in any fashion at the moment, and I'm looking forward to seeing what this is about as much as anyone.