He's eligible to return next week. He's not likely to return next week, either. In fact, Tribune Review reporter Mark Kaboly is suggesting optimism of DeCastro's return this year, while present in August, has waned a bit. He said offensive line coach Sean Kugler told him DeCastro's return is on his timetable, suggesting he won't be rushed back.
Least of all not when the Steelers offensive line is playing as well as it is. Perhaps that's sort of evidence that the Steelers weren't optimistic about their offensive line this season. With it being a reasonably solid unit (with tempered enthusiasm heading into a tough game in even tougher conditions this weekend), there's no urgency surrounding a prized draft pick returning to play midway through his rookie season.
Nothing changes at all if he stays where he is, and all signs seem to be pointing toward his first season officially happening next year.