Willock has been on loan at Newcastle since the January transfer window and has enjoyed a brilliant run of form.
The 21-year-old midfielder scored for the sixth game in a row this week, netting the winner against Sheffield United, and the Magpies want to keep him.
The club hope they can land the Hale End academy graduate for around £20million this summer and make his move to the north permanent.
But asked whether Willock will be an Arsenal player next season, Arteta said: “For sure because he’s got a contract and that’s going to be here. That’s for sure.
“I am really happy that things have gone so well because of the potential that he has. I think it was great for him to go away and have a different experience.
“He has grabbed that opportunity in a really positive and remarkable way and he will come back to us, we will have a conversation with him and plan the next years for him.
“And he got the responsibility and the test of going to Newcastle to help them get where they want to. I spoke with the coaching staff there and they are extremely happy because he was a key part of contributing to get the objectives that they had. That’s a real positive for him.”