Will the 7950 and 7970 be getting mantle support?
Yes. All cards with GCN Architecture 2.0 will support Mantle. I'm pretty sure that all 7000 cards have it.
Indeed. Also, AMD have come out and said that Mantle will not be exclusive to AMD. Not sure if that means it will be compatible with other architectures.
One can only imagine if Mantle got into the mobile market.