Portuguese defender Soares, currently recovering from a knee problem, is out of contract in the summer and has been linked with a move to Arsenal.
Asked if the arrival of Walker-Peters from Tottenham meant Cedric was now likely to leave, Hasenhuttl said: "From our side, yes. The fact is that he is out of contract in the summer."
The Southampton manager told a press conference broadcast by the club: "We had a good meeting two days ago. We didn't speak about that (Cedric leaving).
"I was very positive with the development of his game in our shape and I also mentioned I could go longer with him (in the team), but sometimes things change quickly in football.
"Then for the club and for him, it is the best that we say 'okay, if you want to leave, you have only two or three more months (of) contract, then it's better to go' and we are concentrating on developing other players."
Walker-Peters, 22, has made just five appearances for Spurs this term.
Hasenhuttl confirmed Walker-Peters will not be in the squad for Saturday's Premier League trip to leaders Liverpool.
The Saints boss, though, is confident the full-back can make the most of the opportunities ahead.
"I think he can learn a lot and if a player wants to come to us a hundred per cent, then he is always welcome," Hasenhuttl said.
"The whole package is something we can develop and this is our goal. It is important for him to learn as quickly as possible.
"He cannot play against Tottenham in the FA Cup (replay), but then we have two good weeks to prepare for the Burnley game and this time, he will need."
Hasenhuttl does not expect any more major business ahead of the deadline.
The Austrian feels Southampton's investment in the potential of youth can continue to serve the club well.
"Here, this is our philosophy. We went this way I think now for more than a year and we see young players developing very well," said Hasenhuttl, whose side have climbed into the top half of the table after just one defeat in seven league games.
"We have a few bright diamonds in our youth. We will have a lot of fun with them."
Southampton will head to Anfield without midfielder Stuart Armstrong, who faces up to three weeks of recovery from a hip problem.
Defender Yan Valery has resumed full training after a viral infection while Jan Bednarek is available again following concussion.