Former Gillingham and Norwich forward Jackson, 28, has struggled to cement a place in the starting line-up since signing a short-term contract with the club in September.
Smith, 24, has featured on 12 occasions, mostly off the bench, since arriving on loan from Swindon in September and Wilkinson has made just three starts in 12 appearances after joining from Bolton in a similar deal in July.
"Simeon Jackson is going to move on," head coach Lee Johnson told the club's official website.
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"He's a great lad and been excellent around the place and consistent in his training and personality, he just needs a run of games, he hasn't really had the opportunity."
Johnson said both Smith and Wilkinson had struggled to make an impact at Oakwell.
"Michael Smith will be going back to Swindon," Johnson added.
"We had a pre-set transfer in place for him but he hasn't played as much as he would have hoped.
"There are times he would have started like JPT games but he couldn't because of the restrictions on the loan.
"Conor Wilkinson will be going back. I'm disappointed in him if I'm honest.
"I think he's got all the talent in the world but his application needs to improve.
"He could be anything, but it's up to him. If he improves his ways the world's his oyster."
Johnson said he hoped to extend the loan spells of defender Aidy White (Rotherham), plus midfielders Ben Pearson (Man Utd) and Lloyd Isgrove (Southampton), while he hopes Reece Wabara will sign a new deal as the defender's short-term contract is due to expire on Thursday.
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