We are working on getting drivers out which support the AMD_sparse_texture extension. We really want to make sure the implementation is solid, and so we are being quite thorough with our QA, which unfortunately leads to longer turn around times. We believe this to be beneficial to our users in the long run, though. Watch this space. I'll post here and announce on Twitter once we have the extension posted and drivers shipping.
As for NV_bindless_texture, our GCN architecture could support most of it, but not all of it as it's currently written. We've been trying to think of a way to do something similar with our own hardware, and hopefully we'll be able to do it in such a way to allow it to work on AMD and NVIDIA hardware alike.