Ryan Giggs, 37, has expressed a desire to extend his long United career and Ferguson had hoped 36-year-old Scholes would do the same thing but the Englishman has so far been non-committal.
Ferguson has already started looking for the next generation, including Southampton's Alex Oxlade-Chamberlain who will effectively be on trial in the fourth-round tie.
The 17-year-old has been linked with a move to Arsenal but has also caught Ferguson's eye ahead of the trip to the League One club.
"Yes, the boy's got potential of course, he's only young," Ferguson told a news conference.
"Southampton have done very well over the years bringing young players through and he's another one, along with Gareth Bale and Theo Walcott. Before that ... the two Wallace brothers, Alan Shearer, so they've been good at that over the years. They are doing a lot right."
Scholes said this week that he did not know what he would be doing next year.
"Paul's not made up his mind," said Ferguson. "I hope he stays on for another year, I think he can do that. But I will leave it with him."
FAMILY BEREAVEMENT
Scholes could play on Saturday but defender Patrice Evra will miss the game due to a family bereavement and goalkeeper Edwin van der Sar will not travel to the south coast.
Midfielder Michael Carrick, who missed the Premier League leaders' dramatic 3-2 comeback victory over Blackpool on Tuesday with an ankle injury, should be fit.
The match pits United against the club they lost to in the 1976 FA Cup final when then second division Southampton sprung a major shock.
The Saints are challenging for promotion and Ferguson was impressed when he watched them in a 6-0 victory over Oldham Athletic this month in which Chamberlain scored.
"They are having a really good season, it won't be an easy game," Ferguson said.
"Away games in cup ties are never easy anyway so it should be a difficult but exciting game too because they definitely play good football and they have a go."
