Do you think that in the next two books we might learn more about Thais's POV, or characters like Anush Joshi, or even possible "siblings" who are Ash's friends?And regarding Kit, do you think we'll see him forming new friendships or closer connections throughout the story?
We have Thais' POV in the first book as well as, once, the POV of one of Ash's friends. I can see why people are curious about Anush and whether Kit has friends because very little is known about what these folks have all been up to in the years in between TDA and TWP, so it is natural to speculate about people whose names you know. Might they be important to one of our folks? Thais is important to Dru, and Anush is clearly friends with Ty, but otherwise, we don't know.
And unfortunately the answer is I can't really tell you. I can say over and over that this is Kit and Ty and Dru and Ash's story and the others are supporting characters, but even then, there's going to be an attempt to figure out a heirarchy of supporting characters. I know that. :)
None of this is unusual, it's the product of waiting a long time for the continuation of a story! You start to imagine what might be in it and build theories around that. I've done it myself. I can only say that there's no way to really guess what happens in a next-book-in-a-series because there can always be a new character, location, or plotline that has never been hinted at.
I will say that TWP is something of a unique case in that not only do we have our main four, but we have Thais, Jaime, the entire cast of TMI, the entire cast of TDA, and a chunk of the cast of TID as well as characters from TEC who all have to play some part in the story and be relevant. So I think this is a slight situation of Be Careful What You Wish For. Would it be fun to get to know Anush better? Sure! Would it be worth it if it takes pages away from Kit, or Ty or Dru? Or Magnus or Alec? Or Clary or Jace or Jem or Emma? Or the meaningful development of a different complicated relationship, like the one between Kit and Ash? Because that's a real choice that has to be made — alas, books cannot have infinity pages, even if we want them to. :)
(As for Kit and friends, Kit is dealing with the issue that he is distant (by design) from most Shadowhunters, and his mundane friends (who we know about, plus the maybe werewolf girlfriend) don't know he's a Shadowhunter so he can only be limitedly close to them. The big thing he's dealing with really is what it means to be the Heir, the descendant of Auraline, and have a power that is both useful and that he resents as something that keeps him apart from most other people. It's not as if he avoids friendships entirely by choice, really.)