England will complete a clean sweep of victories over southern-hemisphere heavyweights Australia, New Zealand and South Africa on successive weekends if they beat the Springboks in Saturday's final.
The 2003 England World Cup winner Dallaglio is enthused by what could lie ahead for Eddie Jones's squad.
"This is a team that is still very much discovering how good they can potentially be," said Dallaglio, speaking on behalf of Land Rover, Official Worldwide Partner of Rugby World Cup 2019.
"The exciting thing is there is a lot more to come from this England side.
"They have now set that benchmark with that performance (victory over New Zealand in the semi-final) right up there, and it's going to be something quite special, I think.
"To win a World Cup, two of your games normally tend to be against southern-hemisphere teams, but were they to beat all three back to back... I am not sure I can recall that.
"It's pretty impressive, but they have got one more to go, and that's the key."
Reflecting on England's stunning victory over the All Blacks, Dallaglio added: "It's one of the all-time great Rugby World Cup performances, full stop.
"I would almost go as far to say it was the most complete England performance we've seen for quite some time, if indeed ever - and I say that with a huge amount of pride.
"I think what was even more impressive is that normally when you see a team beat the All Blacks there tends to be a lot of hysteria on the final whistle because it's a major achievement.
"But I think with this side what was really impressive is that at the final whistle, yes of course they were pleased - there were big smiles, big hugs and everything - but they seemed to be fairly grounded and under control and recognised that it was a semi-final and not a final.
"That is a good sign for this England team.
"If they go on and win it - and it's going to be a very tough game - to have played the three southern-hemisphere teams on consecutive weekends, I don't think anyone could deny that they would deserve to win the World Cup."
Dallaglio is wary of South Africa's threat on Saturday as they bid for a third world crown following successes in 1995 and 2007.
"We can't expect that they (England) are just going to go out there and do necessarily what they did to New Zealand," he said.
"South Africa have proved they are a very difficult side to beat. They have only conceded four tries in the whole tournament, with two of them being against the All Blacks in their first game.
"They are a tough nut to crack, and they are pretty determined as well. Given what England did to New Zealand, they will be favourites in terms of the way they played, but it is going to be difficult."
If England conquer the rugby world this weekend, similar scenes to 2003 can be expected such as a London victory parade and Downing Street reception.
"They will have achieved something very, very special that is very hard to do," Dallaglio added.
"I remember from my own experiences, you celebrate it with the country - it's an amazing achievement and everyone feels very proud.
"If you can start your season by winning the World Cup, then the possibilities are endless after that."