Hello, Late Watcher: Thought I'd do my best to help in some way. (I've been an obsessed "Alias" viewer since the very first episode [which aired just a few weeks after 9/11] and haven't missed an episode. Alas and alack--as you well know, there'll be no more episodes).
Although I don't know how you feel about spoilers--you do ask most pertinent questions--I'll say that, yes, you're correct (and it's well known in the Aliasverse) that the actress Lena Olin wasn't available for the third season--reasons much discussed by myriad posters. There was much poster speculation that Jack might not have been corresponding with Irina, but instead he was communicating with her sister Katya (whom you mentioned). Then again, Irina/Katya cut off Jack's queries abruptly--as the series' timeline wavers through time and space--but I think you will find out what I mean viewing the Season Four finale (not my all-time favorite),
As far as your questions regarding future storyline developments (or non-developments, as the case may be), I would advise you to read AA's Verdantheart summary of each epispde, and, of course, then you can flash ahead. After viewing each episode, I couldn't wait until she posted each summary. However, I was even more enthralled (I'm a Lit major) with her emphasis on characterization analysis and "family." (Well, we didn't always agree on Vaughn, but we certainly did concur on Jack [and Lauren.]) I might add that she in turn, received page upon page of thoughful replies and opinions to her "Discuss" queries: Spydancer, Azalea, oh the list goes on.
I also would advise you to go the wonderful TwoEvilMonks Web site--which posted images and wry, humorous captions of each episode up to and including the first episode of Season Five, "Prophet Five." I don't have any notion how long Ephian will keep the Web site "on," but here is the "address" I use:
HTTP://www.twoevilmonks.org/aliascatacombs.htm/ Hope this helps. -- Persimmon
