If you play akshan to steal opponent gear and attach shady spectacles to akshan does the gear will never return?

No — the stolen gear still returns when Akshan leaves the board. Attaching Shady Spectacles and making Akshan a copy doesn't make the steal permanent.

Akshan's "You control it until I leave the board" creates a delayed control-change effect the moment his trigger resolves. That effect was already generated and keeps applying even if Shady Spectacles overwrites Akshan's text by copying another unit (Rule 392 — delayed abilities persist regardless of their source's state). So the copy doesn't remove or extend the control window; when Akshan leaves the board, control of the gear reverts to its original owner, and if it was Equipment attached to him, it detaches with him and returns to that owner.