For what reason are you interested in that? Any such algorithm would have to make use of the re-programmability of FPGAs, since a static FPGA layout can always be turned into an ASIC...
My interest really has nothing to do with cryptocurrency, but I've been reading about dynamic method migration[0] and modular reconfigurability[1] for a long time. I can see how some of my professional work could benefit from 'adaptive computing'[2] trends as well. The algorithm I have in mind would simply be geared towards hardware that I want to own already.
[0] http://dx.doi.org/10.1109/IPDPS.2004.1303105
[1] http://www.doc.ic.ac.uk/~tbecker/papers/iee06.pdf
[2] http://www.cray.com/Assets/PDF/about/IDC-AdaptiveSC.pdf