"Criminal Minds" season 11 has gone on floor and the production is going on in full swing for the upcoming season, which is set to premiere on 30 September. And the detective series is expected to witness various changes in the cast and plot.

While show's usual cast will return for sure, the FBI Behavioral Analyst Unit (BAU) will also have some old faces making a comeback and new faces joining in. In fact, fans will get to witness guest appearances as well.

"Criminal Minds" season 10 saw Kate Callahan (Jennifer Love) resigning from BAU to spend time with her family. This plot was introduced for Jennifer's exit as she was pregnant in real life. Similarly, even AJ Cook, who plays JJ is on maternity leave.

After the exit of these two popular faces from the show, fans have been speculating as to who will fill this void. And that's when show-runner Erica Messer confirmed that they will bring back old characters, introduce new ones and plug in exciting guest appearances to keep the show going.

Though there's no confirmation on when Love will join the cast, Cook is said to return after missing a few episodes in season 11. Apart from this, Aisha Tyler from "The Talk" is confirmed to be a part of the upcoming season.

Tyler will play the role of Dr Tara Lewis, a forensic psychologist, who is interviewed by Hotch and gets confirmed as the best replacement for Kate Callahan's position. Tyler is also rumoured to be Dr Spencer Reid's new romantic partner.

There are also speculations that Marisol Nichols from "NCIS" will be joining the cast of "Criminal Minds" and will reprise the role of Agent Zoe Keat. But this rumour looks unlikely to come true, as the two shows get aired on two different networks.

Recently, when fans got in touch with Joe Mantegna (David Rossi) and Esai Morales (Mateo Cruz) through Reddit's Ask Me Anything (AMA) session, the actors confirmed Paget's appearance on the show. "Well, there's been talk of — there's a chance Paget may make an appearance now and again. Eric our producer mentioned it in an interview that there's a possibility that Paget may return from time to time," they said.

But, the latest reports suggest that fan-favourite character Jane Lynch will make a comeback. Messer hinted that Lynch will appear in more than one episode in the upcoming season, reports Cinema Blend.

"With "Glee" finished and (Lynch's new show "Angel From Hell") is on CBS ... I don't think that will be a problem. We absolutely want her back. I've talked to Matthew about it. We've got to find a reason to bring her back because I don't want it to be unrealistic or just to have her. And we want to be able to use her well too," she said.

Lynch plays Diana, who is Spencer Reid's mother and is dealing with schizophrenia. "She was doing well last we heard, which is great. But often with the drama shows, you need a dramatic reason that she's back, so we're going to figure that out first," Messer said.

As far as guest appearances are concerned, "Criminal Minds'" Twitter account dropped a major clue that Jackie Chan may be featured in season 11.

The caption read: "@EyeOfJackieChan said 'coffee is a language in itself' @ the 2006 opening of his coffee franchise #CriminalMinds."

Twitter/ Criminal Minds

Meanwhile, there have been speculations that the plot of the next season will take fans deeper into the lives of its characters. In an interview with Digital Spy, actor Matthew Gray Gubler (Spencer Reid) hinted that he would be interested to go deep into the character he plays.

"It's always fun when the writer takes a magnifying glass to the characters' lives. I'd love to delve more into his home life and his social life and to see his mother return and just to... kinda like... figure out what he does on weekends," the actor said.

The 67-year-old actor added that there's going to be more personal stories and character development in the episodes on season 11. "I've been married three times, we've dealt with two of my wives so far, so there's a possibility you might find out more about wife number three," he said.

It has been reported earlier that CBS will push "Criminal Minds" by an hour during Wednesdays. And that the show will swap timeslots with another primetime show "Extant".

"Criminal Minds" season 11 returns on CBS on 30 September 2015.