Yeah, while I do not expect a full class storyline, I think there is other ways they could go about doing it. Perhaps certain characters from the class stories make appearances in a faction arc, with special interactions for the corresponding class.
Maybe even short, post- Tython/Korriban style conversations with one of them, during or after the questline. Ideally, with dialogue from a relevant companion character. (eg. Tai and Zenith).
Personally, I'm dying for something. That letter was such a tease.
Yeah...it's not what I want, but I could go for that!