The Black Cats have been left short of forward options due to Nathan Broadhead’s hamstring injury, which will leave the Everton loanee sidelined for at least three months.
Harris and Kimpioka, both 21, have been included in recent matchday squads, with the latter coming off the bench to score against Sheffield Wednesday.
When asked if the pair could make an impact in the second half of the campaign, Stewart, who is the top scorer in League One with 15 goals this season, told the Echo: “I think they have shown that.
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“Will has been given his chance a couple of times in the first team and Benji came on and scored.
“They can both do a job when asked upon and training with them both I think they both have good futures in the game if they keep doing the right things.
“They are at a really good age where they are still learning and still developing so a lot of it will be down to how much work they put in and how hard they work, how much they want it in a sense.
“Training with them everyday you see the bits of quality that they have and I’m sure if they keep doing the right things they can have good careers in the game.”
Sunderland’s 5-0 win over Wednesday marked a stark contrast to when they were beaten 3-0 at Hillsborough in November.
Stewart was part of that chastening defeat but feels the Black Cats’ young squad have learnt some valuable lessons to subsequently go on a nine-match unbeaten run in the league.
"I think down there it was really tough but I think we’ve shown how much we’ve learnt in the short period in terms of managing the game and doing the right things,” admitted Stewart.
“It was a tough night when we were down there but I think you’ve seen the difference that we have shown.
“We have come a long way in a short period of time and at the same time we still have plenty to build on and that is probably the exciting thing, we still feel there are levels to go up.”