I think Highsmith is likely to be departing Pittsburgh soon, but this still feels like a 2027 move to me. He would be an outstanding element across from Bosa, but with the 49ers investing in young D-line players over the past two years, I’m not sure you want to displace their progress by taking snaps away.
Still, Bosa, Osa-O and Highsmith, adding in Williams, Height, Collins and West, all on the same line, would wreck some offenses.
I’m still projecting he goes elsewhere, and probably next season, though.