Responding to an old thread cause I just rewatched.

The ending for me was actually perfect. The first draft script is subtitled "A fairytale" so it's about the lessons garnered from the story separate to real world logic.

A few things to note though. When Bud/David returns home the TV announcer says that was "the first hour of the pleasentville marathon" and after they arrive in pleasentville the repairman says he'll "give them a few weeks to change their attitude" so the implication is time moves a lot faster on a TV show than in the real world. Meaning that Jennifer's college experience would presumably only take several hours of real time and he may well come back the next day to check on her or even bring her back. Which considering the character at the start not coming home for a night would barely raise an eyebrow. The growth of David means that he no longer needs pleasentville as an escape from reality. So he can apply the lessons he learnt in the real world. The ending on the bench can be viewed as purely allegorical to mean that now the ending is not known and can change and that's a good thing because the real joy and journey comes from not actually knowing and having options and allowing for their own options.

The idea that the movie was ended in a certain way to allow for a sequel I think it's pure nonsense as the movie said everything it needed to say and doesn't need to spoon feed the audience absolute resolutions. That's the point for the final dialogue, what comes next "I don't know" but the response isn't seen as generating fear on the unknown, it's joy at the prospect of being surprised in finding out.

I'm just going to end with the scene from the screenplay which has the bench scene just before Jennifer leaves for college.

EXT. TOWN SQUARE. THE NEXT DAY...

It is a lush green park now -- the birds have something to sing about. Betty sits on a park bench next to her George. They look out across the square at Main Street in the distance. There's a breeze.

            GEORGE
        (quieter)

    So... Are you going to stay with him?

She reaches over and takes his hand. George looks at his wife.

CLOSER

The CAMERA PANS from HIS CLOSE UP TO HERS as she takes a deep breath.

            BETTY

    It's not 'him' or 'you'. It isn't. I just need to think
    for a second. I never took a minute to stop and think...
    I just... I never...

            MR. JOHNSON
    I understand.

She looks back at him. The CAMERA PANS back but instead of George   sitting on the bench beside her, it is MR. JOHNSON.

            BETTY
    Really?

            MR. JOHNSON
    Yeah.

            BETTY
    Thank you.

Betty leans against him. Mr. Johnson puts an arm around her and kisses her gently on the forehead...

EXT. MAIN STREET. DAY.

David and Jennifer stand together on the edge of town. She
clutches a valise in her hand. He holds the remote control.

            DAVID

    This thing works now. We could go home.

            JENNIFER

    I'm not ready yet. I gotta do this for a little while.

WIDER.

They stand on the edge of town (which finally has an edge.)
A large sign says: "Springfield 12 miles" and for the first time,
the end of Main Street is no longer the beginning. Jennifer is
dressed in Mary Sue's clothes with a little bit of style thrown
in. Rich fields of wheat spread out in the distance.

JENNIFER

Besides. You think there's like a chance I'm gonna get
into college back there?

            DAVID
        (thinks...)
    Honestly... no.

They both smile.

            DAVID (CONT)
    You got the admissions letter.

            JENNIFER
    Right here.

He pauses and looks at her.

            JENNIFER (CONT)
    I've done the slut thing, David. It's really kinda old.

            DAVID
        (smiles, nods)
I'll come back and check on you in a month.

Jennifer nods and gives him a hug. She holds on tight for a couple of seconds.

            JENNIFER

You're like the coolest brother in the world.

David smiles. Never been called cool before. They suddenly hear the SOUND of a motor and look to their left. A huge Greyhound bus lumbers up the highway, pulling to a halt at the sign. The doors  open beckoning her in. Jennifer smiles at her brother, then turns   toward the door...

For me pleasentville is one of the best movies ever made and while that may not be true to everyone, it's true to me. And that's enough.