The 22-year-old has come in for regular criticism during his two seasons in England but has recently helped United keep six successive clean sheets as they seized a firm grip on the Premier League title race.
The Spaniard was also nominated for the Premier League player of the month award for March.
"David has developed and matured as the season has gone on," said Ferguson. "We've seen a very progressive and developing young goalkeeper and next season he'll be even better."
Another member of United's defensive unit, Rio Ferdinand, believes there were a number of factors that made it difficult for De Gea during the early days of his time at Old Trafford.
"When you are a keeper, experience comes with games and becoming used to certain situations," said the veteran defender. "He hasn't been here long. He is young, he had to become accustomed to his new surroundings and he wasn't given time.
"When you play for Manchester United you are under incredible scrutiny. That is just the way it is.
"You have to get used to it. You need a thick skin to be a Manchester United player. Because if you cannot take a battering at times you will fall by the wayside and someone else will fill your shoes.
"He has a huge price tag on his head that carries a lot of weight. But he is resilient, even if he still has a lot to prove because this season is not over yet."