To me there is no clear cut answer to that that question. I could make a case for either one. It all depends on how the draft goes but there's no way I cut him before then; doing so forces your hand in the draft and the Steelers don't normally like to operate that way.
What if you cut Hampton and you miss out on Poe, Martin, and then Ta'amu, then you're royally screwed.
I would love to see them take 2 Guards in the draft this year, hell spend the whole draft on the offensive line but either way I'm just not convinced you can release Casey before training camp.