This deal is extremely unlikely to happen, as nobody just offers up top tier young wingers or D, unless there is a situation that forces it.
The Leafs have no reason to trade for Trouba without having a clearer contract situation. They can't officially sign him until Jan 1 if they did, no way they are moving Nylander for that much risk if they feel Trouba could force his way out.
The Jets don't need to trade Trouba right now. He plays the position they need the most, as they have no one capable of doing what he does in the system where as they have Rosovlic potentially able to be the center they need. Jets are better off just using up this last year of Trouba and moving him next summer. Maybe they get a little less at that time, but it's worth taking a run at it with him in the line up for a team that is a definite contender.
In the very short term, the Leafs would improve more from this deal than Winnipeg. Toronto's hole at RD is large, and no one really likely to fill it in the next 12 months. But having the situation they have now, with two top 10 centers playing with high end wingers is a big appeal to their depth, so it's not as if it comes without a cost, and the Trouba situation makes it difficult to know if you are getting long term value.
The Jets hole at 2C is a little exaggerated, and Rosolovic could step in and if not take that role, he could insulate Little enough by creating a great 3rd line that it's a non issue. Nylander is likely more talented than either, but still not a proven commodity at C, and he has far less value to the team as a winger, so in the short run, there isn't enough to gain.
I saw a comment about the Leafs leaking these rumors, but it came from Eklund. Nobody leaked anything, it's just that everyone has been talking about the Leafs trading one of Marner or Nylander for help on D for awhile, and now that Marner has had a great season and strong playoff, Nylander is the whipping boy in these discussions. I very much doubt there has been any discussion about trading Nylander. If they were open to the idea, he would likely be playing in Calgary right now and the Leafs would be trotting out Hamilton on the right side to start the season.