Filch, Umbridge, and Fudge apparently thought Peeves could be expelled, as we find towards the end of Order of the Phoenix:
But when Educational Decree Twenty-nine comes in, Potter, I’ll be allowed to do them things... And she’s asked the Minister to sign an order for the expulsion of Peeves... Oh, things are going to be very different around here with her in charge..."
Filch had also expressed the possibility of expelling Peeves back in Goblet of Fire, when he found Harry's egg:
"Hiding, are you?" he said softly. "I'm coming to get you, Peeves.... You've gone and stolen a Triwizard clue, Peeves.... Dumbledore'll have you out of here for this, you filthy, pilfering poltergeist...."
"The thing is, Professor," said Filch plaintively, "the headmaster will have to listen to me this time. Peeves has been stealing from a student, it might be my chance to get him thrown out of the castle once and for all —"
Fleur Delacour also assumed that a poltergeist could be expelled, judging by her statement to Roger Davies at the Yule Ball in Goblet of Fire:
We 'ave none of zis ugly armor in ze 'alls, and eef a poltergeist ever entaired into Beauxbatons, 'e would be expelled like zat." She slapped her hand onto the table impatiently.
However, the mere fact that various characters believed it to be possible doesn't necessarily mean that it actually is possible.
On the other hand, it would make sense that Peeves could be expelled. We know from Percy's comments when they go to Gryffindor Tower for the first time in Philosopher's Stone that Peeves more-or-less listens to the Bloody Baron:
"You want to watch out for Peeves," said Percy, as they set off again. "The Bloody Baron's the only one who can control him, he won't even listen to us prefects. Here we are."
If there was nothing the Baron could do to Peeves, Peeved would have no reason to be afraid of him.
Additionally, there was another discussion between the ghosts about Peeves prior to the opening feast in Goblet of Fire:
"Peeves, of course," said Nearly Headless Nick, shaking his head, which wobbled dangerously. He pulled his ruff a little higher up on his neck. "The usual argument, you know. He wanted to attend the feast — well, it's quite out of the question, you
know what he's like, utterly uncivilized, can't see a plate of food without throwing it. We held a ghost's council — the Fat Friar was all for giving him the chance — but most wisely, in my opinion, the Bloody Baron put his foot down."
This implies that there is some method that is capable of keeping Peeves out of the Great Hall, for otherwise Peeves could have just entered despite the protestations of the ghosts. If there is a way to keep him out of the Great Hall then there should also be a way to keep him out of Hogwarts entirely. If there was no way to physically stop Peeves from entering the Great Hall then there would be little reason for him to not enter out of fear of the Bloody Baron, because there would then seem to be nothing the Baron could actually do to him.
Furthermore, we know that spells do work on Peeves. During the first Defense Against the Dark Arts Class in Prisoner of Azkaban Lupin uses a spell on Peeves when he refuses to obey him:
He raised the wand to shoulder height, said, "Waddiwasi!" and pointed it at Peeves.
With the force of a bullet, the wad of chewing gum shot out of the keyhole and straight down Peeves's left nostril; he whirled upright and zoomed away, cursing.
If Peeves is susceptible to such magic it would stand to reason that there is some magic that would be capable of removing him from the castle. We certainly see Peeves physically interacting with things throughout the books, so it should be possible to physically move him.