Jim Parsons and Johnny Galecki Jim Parsons and Johnny Galecki

Leonard and Penny may have finally gotten engaged on The Big Bang Theory, but bigger developments are in store for Thursday's Season 7 finale (8/7c, CBS).

"There are a lot of moves made by different people in the finale," executive producer Steve Molaro tells TVGuide.com. "This season is more of a cliff-hanger ... and what happens affects everyone, not just one person."

Scoop on 39 must-see finales

But the focus will be Sheldon (Jim Parsons

), who, unsurprisingly, is struggling with all the changes in his life. After having an epiphany about string theory and losing his childhood hero Professor Proton (Bob Newhart) two weeks ago, he'll face some professional and personal shakeups in the finale. It starts when Caltech won't let him change his field of study, and it's exacerbated when Leonard (Johnny Galecki) and Penny (Kaley Cuoco-Sweeting) discuss new living arrangements, aka moving into a new place sans Sheldon. "He's really struggling at a crossroads in not just his career right now, but all walks of life, which is also taking up a lot of his focus above and beyond his relationship with Amy [Mayim Bialik]," Molaro says. "She's trying to do her best to help him move on and get through this, but everything is really rattling him."So what's a change-resistant scientist to do? Sheldon will make a major and literal move in what Molaro describes as a watershed moment for the character who's so fixated on ritual and order. "A lot of things in Sheldon's world aren't the way they normally are and there's nothing he can do to make them go back to the way they were," Molaro says. "He realizes that and that's big. ... He couldn't have done that a few years ago. We always say these characters develop at a glacial pace, but when it does happen, I think it's pretty momentous. We felt like it was the right time to do this."Another watershed moment will come for Raj (Kunal Nayyar). When we left Raj last week, he was making out with Emily (Laura Spencer) as they discussed showing each other their secret tattoos. Even Molaro is slightly surprised at how quickly the duo's relationship has progressed since Raj finally learned to talk to women sober at the end of Season 6. "Their chemistry is great and we just went with it. I'm really enjoying their dynamic," Molaro says. "With Emily, unlike all the other girls he's gone out with, he's just being flat-out honest. It sounds like it's something he shouldn't say in the moment and it's this honesty that she finds so charming about him. For some reason with her, it's working. I think this newfound confidence is growing because of that. Again, it's taken a while, but it's worth it when we get there."

Add new fall shows to your Watchlist!

The Big Bang Theory will have a lot of time to get wherever it's going, after receiving a three-season renewal earlier this year. But Molaro says producers will continue to refrain from plotting long arcs. In fact, he says they currently have no idea how Season 8 will open, or where Sheldon will be."We don't work in long-stretching stories and we never have," he says. "One episode bleeds into what the next will be and we haven't thought about next season yet.  I just want [fans] to enjoy the finale and then we'll start focusing on the next episode. I can't predict how fans will feel; I hope they like it. It's a little bittersweet, but there are a lot of nice moments."The Big Bang Theory airs Thursdays at 8/7c on CBS. Watch last week's episode here.(Full disclosure: TVGuide.com is owned by CBS.)