He will be eligible this winter for the Rule 5 draft, as will any 2017 or earlier Highschool Draft Selection/Int signing and 2018 or earlier College Draft Selection who isn't on a 40 man roster.
It's highly unlikely he is added to the 40 man roster, the Reds are not going to have many spots open once they have to re-add guys on the 60-Day IL even after the upcoming free agents are removed. Additionally, very unlikely that he is plucked during the draft.
There are hundreds and hundreds of players eligible each year, only a dozen too a dozen and a half are selected. Over the past decade fewer than 6 per year have been selected and made it through the season with the team that selected him