For me, last scene in Trespasser gave me the feeling the IQ will be involved in the next game but probably not playable. I saw the last scene as setting up for a new protagonist to be an "agent" of the organisation the IQ has to track, find and stop Solas. I personally would like some involvement because regardless of which IQ I played, my IQ's kinda feel a tad responable for Solas especially had she known she may of been able to stop him while he was still weak. I think if there was a "sacrifice" scene with Solas, the IQ may show up *shrug* I dunno, I didn't really get the resolution that some of you got. In the end I'd be happy if the IQ is a chessmaster and new protagonist is an agent and because of your decision as IQ to redeem or stop Solas, different quests are available/given.
If my Trev has a cameo aswell, I kinda hope Cullen is left at home... that way he can't be hurt 
As for my Lavellan, I want closure for her but I'd still be happy for the above to happen. I think my Lavellan, though still in love with Solas, took the ending as his final goodbye... as in you won't catch me & if I succeed, one of us or both will be dead. I personally do hope that the IQ gets a cameo at least to help kill/save him.
Also I kept her valleslin because she still felt a connection to the Dalish & still saw it as an integral part of herself but realised after everything that had happened she could no longer go back. She didn't really feel lost afterwards just different. She doesn't really see her role as too different after disband, I've headcannon that still does still search & try to redeem Solas (though she doesn't find him personally) and instead of becoming Keeper of her clan, she's kinda like Keeper of the people who stay with her etc She does stay in contact with her clan & trusts them completely - infact I've headcannon some of them spying for her on Solas' little operation 
EDIT: Also for me, I don't see Solas as the villian but antagonist - yes. I wouldn't be surprised if the veil is brought down and then the Evanuris become a far greater probelm.
Kinda hurts thinking about it, cause it's so open and I have no patience for it atm, I want DA4 now!
Also I can't remember who (think Riverbanks) mentioned about the Wardens. What I found interesting in my Trev PT with being friends with Blackwall & having sent him to the Wardens after the breach, he mentions in passing that there is infighting in the Wardens and that he fears or wouldn't be surprised if they tear themselves apart from the inside. I should look for the exact quote... makes me wonder if they'll have any involvement in next game. Something else gave me hope about griffions too... I think he sends a letter or something later (my memory is shite atm) but includes a griffon feather. I might of watched someone else's ending on YouTube, might be after he leaves his LI in epilogue.
I'm looking forward to Magekiller too
I went into my local comic book store & already have a standing order for it (I like to actually hold it lol) and with the next game looking to move to Tevinter wondered if the main characters will appear in the next game. Also, if Maevaris & Dorian possibly making an appearance in the comic. Without know really anything about it, I have speculated that prehaps they become agents for Maevaris/Dorian's resistance and in turn have some involvement in DA4.
I will be disappointed if Dorian and Maevaris don't make an appearance in a game set in/around Tevinter.
Ugh, I'm so tired so if none of this makes sense I sorry. I spent at 30minutes today running around the school looking for a lost kid on a hot sunny day only to find him in the 2nd last classroom I check (after checking EVERYWHERE else) to get "I got confused"... sneaky bugger just wanted to play games on the laptop. It's taken a lot out of me... for various reasons