Sir Alex Ferguson is convinced that the current crop of young Manchester United players can become the dominant Premier League force in the coming seasons and has warned his rivals that the Old Trafford club are "not going away".

The Scot, whose side are closing on the title with eight games of the season left, also seemed to hint that José Mourinho will return to Chelsea for a second period as manager and, if so, that the London club could provide the key challenge to United. Regarding his current side, Ferguson said: "We've got a lot of youth in the team, there's no doubt about that. The record over the last 20 years tells you we're not going away. So I'd expect us without doubt to have a real good challenge next year.

"Plus we'll have players who are maturing nicely. Rafa [da Silva] has proved how much he's developed this season; the goalkeeper David de Gea's progress right through the season is absolutely superb and he'll get better next year. [Shinji] Kagawa will be a far better player next year, I'm certain about that. We have to deal with the fact that one or two players are getting older, but I think we're not so bad in terms of protecting most positions. So we're not going to go away, no doubt about that."

Ferguson and Mourinho are the only managers to have retained the Premier League title and the Scot acknowledged it will be difficult to repeat the feat. "Whether we can go on another run of three titles in a row, who's to say? But the material's there, it's a hard league, as we all know," he said.

Ferguson also appeared to suggest that Mourinho will replace Rafael Benítez at Chelsea in the summer. "You'd expect – if José goes back to Chelsea – a big challenge there.

"[Manchester] City won't go away, with the money they've got. And I think Arsenal will improve – there's some indication that Arsenal are building a better squad than people think and Tottenham have been progressing for a couple of years now. So it's a hard league to win, there's no doubt about that. But at this moment in time we just need to concentrate on winning the league this year."

With City trailing United by 15 points in their title defence, the City manager, Roberto Mancini, is aware of which departments of his squad need strengthening in the summer. "We know each position but I cannot say this," he said. "They [United] deserve to win this title but next season will be different."