Unique tier upgrading

Not sure if this has been asked before, but anyhow I am just curious.

Will there ever be a way to upgrade uniques? From tier to tier? Unless it would be overpowered, it would be understandable, but I would assume even if you upgrade them there would be a drawback involved reducing its power.

Hope this is answerable. hehe

Probably not. Typically the unique is tied to whatever tier it is.
That way you have a range of uniques of varying types across every level range. Of course, I could be wrong and it'd change in the future.