Ta'amu really had shown very little prior to his his legal debacle, and has been something of a disappointment overall, given how excited the FO was during the draft when he dropped to the 4th round.
TBH I was kind of surprised they kept him--some Steelers beat writers were expecting an outright release. Then again, some of those same beat writers reported that Ta'amu was just about the last person they expected to have the sort of incident he did...so maybe that, combined the need for depth at NT, contributed to him getting a PS spot.
It's tough to know the potential of a rookie Pitt defender after just half a season, particularly in Pitt's defense, which is typically too complex for a rookie to absorb. Otherwise good physical talent can look tentative and confused during the "redshirt" year. (Ta'amu is not in the same universe talent-wise as Troy, but it's worth noting that even TP looked terrible his rookie season). But to be clear, this is NOT a guy you can just plug into your DL rotation and expect to contribute. This is a project IMHO.
Whatever happens football-wise, I hope he gets his life together. He could have killed someone (or himself).