Michael Vaughan sees no other Ashes outcome than a 5-0 series defeat for England and has expressed his concern about what lies further ahead.
Australia regained the urn after an innings and 41 run victory over England in the third Test at Perth, moving into an unassailable 3-0 lead in the five-match series.
England will now go into the remaining Tests at Melbourne and Sydney seeking to avoid a third series whitewash in Australia in their past four trips.
But 2005 Ashes winning captain Vaughan told BBC Test Match Special: "I don't see anything other than a 5-0, I really don't."
Regarding what might follow this series, he added: "The problem when I look at the England team is they are going to go through that tricky position very soon where they have three really senior legends in the team - Alastair Cook, Stuart Broad and Jimmy Anderson.
"You look at the Australian team and there are none of those players retiring for a good few years. They will stay together and get better and better.
"Decisions have to be made moving forward about what is going to be in the best interests of the England Test match team.
"I still think all three will play a part in 2019 (the next Ashes series, in England). It's just, over the next couple of years, they will probably disappear and it is what is to come after them.
"They are going to take some replacing, and that is going to be the difficulty for Joe Root, the management, Trevor Bayliss, how they manage that situation."
Captain Root spoke after the Perth Test of the defeat being "bitterly disappointing", as well as stressing how important it was not to "panic or make hasty decisions", while England coach Bayliss found himself defending his position.
"It's bitterly disappointing," Root said.
"(But) they tried absolutely everything. It wasn't for the lack of effort.
"I don't think these three games are a fair reflection of how we've played and what we're capable of.
"Probably the biggest thing that has been to my detriment is trying too hard. I've been desperate to win this series.''
Asked about the meagre contributions of old hands like Cook and Broad, Root spelled out that he and Bayliss retain faith in players with world-class records.
"It is very important, for me and Trevor, that we don't panic or make hasty decisions,'' Root said.
"We have put up some really good performances in all three matches - simple as that, really - just not for long enough."
When Bayliss was asked if he was certain he was the right coach to take England forward, the Australian said: "I think I am. You may not.
"But I think our performances have done pretty well over the last couple of years.
"That's for people above my pay grade to make that decision, so we'll leave it up to them."