Reports elsewhere suggest the withdrawal is down to Calmac ferries, the not runnings thereof ...
Like you, I found it hard to get a definitive answer out of Scotrail, with nothing on the website, nothing on National Rail ...
It DID include Carlisle.
When I used a SoS ticket last year I got a cheap advance ticket from my start point (MK) to as far as I could get to a centralish point with a cheap hotel (Travelodge in Perth) and started early the next day buying my SoS ticket at Glasgow Central the evening before IIRC- you fill in the dates of use (4max!!) as you go.. Great ticket- I got to Oban and Kyle and would have reached Wick if not for a freight train releted delay... I 'turned back' at Lairg where my train was held. I was hoping to have another go this year, but ... maybe next ...
Hope all goes well.