The Dutch manager wants the midfielder to sign a new contract after another stunning free-kick helped the Cottagers to a 2-1 victory over Martin O'Neill's Sunderland
Dempsey's contract is set to run out in 2013, and clubs will surely be circling for the playmaker this summer after he notched his 17th Premier League strike of this campaign.
"I want to be positive," Jol told reporters. "You are talking about the scenario that a couple of players won't be here. If all the players are here [next season] we will only get better.
"[I'm not surprised by Dempsey] in this game, because I know that he will only get better. You talk to him and he wants to get better because of course he's not perfect, no-one is perfect, but he's improving.
"And after the game we had a little banter because we didn't know he could take free-kicks at the start of the season, so he never took them. Then against Bolton, out of nothing he scores, top corner and he did it again today. So it's maybe something for the future, hopefully here.
"He knows what [the fans] think of him. Hopefully it's enough for him to sign his contract."
Jol also spoke about captain Danny Murphy after the midfielder's wife revealed on Twitter that it could be an emotional day for him in the last home game of the season, perhaps meaning a move away from Fulham, and went on to speak of next week's final game against his former club Tottenham.
The Dutchman continued: "As you saw today, he made us tick again in the first half so I [don't] believe that Danny Murphy has played his last game for us ever.
"There's not a lot of pressure on us [next week]. It would be nice to have three points and I want to say spoil their day, but you don't want that.
"Of course I want Spurs to play in the Champions League. But on the other hand, if we could get three points there we could probably do with them.
"It will be exciting. But I love this excitement. At the start of the season when I saw the schedule, with Spurs the last game of the season, I thought, 'Ooh, err, it could be difficult'.
"And now we have 52 points, we have no problems and we can enjoy the day. You never know. An away game against Spurs, if there is a lot to play for, will be a difficult game.
"I was there. They are quite strong. Now it's only a game to enjoy and hopefully get the three points."
Jol also suggested this is perhaps Fulham's best ever season after making sure of a top 10 finish while also battling in Europe before Christmas.
"It's great to have a win and we will be in the top 10, which was our main target," he continued.
"I'm satisfied with what we have achieved. I think this is probably the best season ever [for Fulham] with the culmination of Europe.
"Of course we were probably higher in the league before, but not playing all these games in Europe.
"Now we're playing all these games, with almost 40 before Christmas and still on 52 points [now], I think that is a good achievement."