Manchester United keeper De Gea is tipped to replace countryman Casillas as Real's number one in 2015-16 in a big-money deal, with the latter often made a scapegoat by the club's supporters in recent seasons.
But Ancelotti, who himself faces an uncertain future in the Spanish capital with Real adrift of La Liga leaders Barcelona, said he has total faith in the 33-year-old international keeper.
"I see myself here at Real Madrid next season, with Casillas and with all of the others who are doing a good job," Ancelotti told reporters on Friday.
"It's not an important question at this point in time. We are focused on what we need to do."
When asked who might be a better keeper than Casillas, Ancelotti said: "It's not for me to list a ranking of goalkeepers; I have three very good goalkeepers who I am happy with.
"The best goalkeepers in the world are the ones I have in my squad. I've never spoken about signing another goalkeeper."
Real - two points behind Barca with seven matches remaining - host Malaga on Saturday.
