The Upper East Side will never be the same.

Speaking with TV Fanatic this afternoon, Gossip Girl executive producer Joshua Safran promised that the May 14 season finale culminates in a major cliffhanger that "changes the fabric of the show forever" and that fans will "realize without a doubt" the ensuing narratives it sets up for next fall ... with one possible exception.

"There's one particular character, you might not know what happens to them," he teased.

He wouldn't say who, or what the unifying storyline of this spring might be, but he did promise me there is one: "All the [storylines] that have continued through the royal wedding are going to land in the same place," he said. "Starting this Monday, you're going to see everything start to come together."

No small feat, considering the number of balls in the air at the moment.

There's Serena, who's been relegated to the back burner for much of this winter, but who's about to begin an intriguing new arc, and who the as-yet-untitled season finale episode "revolves around quite heavily."

With Jack (Desmond Harrington) and Diana (Elizabeth Hurley) set to return, "doors are opened that Chuck was not expecting to be opened," Safran said. "Things happen that change his perspective on who he is."

Several Upper East Siders will be looking to show Ivy the door, meanwhile, while It-Girl-in-waiting Lola (Ella Rae Peck) has no interest in the high society world she was unknowingly born into.

"So much of what we've done over the years has involved outsiders trying to break into this world ... now we have both somebody on the inside in Ivy who doesn't really belong, and Lola, who wants nothing to do with it," Safran added, cryptically noting that the Rhodes girls "may or may not be drawn together by a common bond."

There's also the minor matter of Dan and Blair, a.k.a. Dair.

The fact that Dair has become the most polarizing topic in Gossip Girl history isn't lost on its show-runner, who again insisted there is no "endgame" regarding the couple ... not that he'd tell us if there were.

"People always talk about endgames, but the thing is, if you have have a firm ending set in stone, everything you write runs into that wall," Safran said. "It has to be done with a shifting, malleable approach."

Sorry fans, I tried.

In the short term, we can still expect "the specter of Chuck" to continue looming over the new couple, he adds, with Dan possibly having "a hard time coming to terms with the stresses that brings."

At the same time, Dan "will continue help Blair rediscover Blair in a very sweet, good way," the EP reminded us, noting that she's finally broken the parameters of her relationships with Chuck and Louis.

Safran says Dan and Blair becoming a couple was the plan all season long, too.

"Last spring was the tease," he admitted. "We knew Dan and Blair were going to get together at some point this season, as Dan's feelings for her would only grow, and Blair would grow more aware of them."

"Blair gave up her control, her power in becoming a princess. Now that dream is over, for better or worse, and she's finally breaking free and finding out who she is. And from the beginning, Dan was the one basically saying 'I'll be here always, I accept whoever you are.'"

Currently filming the 24th and final episode of the fifth season, with the 18th airing Monday, Safran says fan backlash (or feedback in general) hasn't shaped any storylines because it logistically can't.

Not that he's unaware of the passions he's stirred in recent months.

"Say anything you want about me, it's my job, but please respect each other!" he joked, calling for civility among the respective camps as the show ramps up for its long-awaited spring run.

Wishful thinking, perhaps. But a nice sentiment.

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.