never … because it’s not possible
all wdtv’s … use hardware decoding (Sigma Chipset)
here are the specs of the Sigma Designs SMP8670AD
http://www.sigmadesigns.com/sdi/wp-content/uploads/SMP8670_br.pdf
so, if H.265 or X.265 is not supported by the chipset … then it is not possible via a firmware update
(hevc decoding needs at least a Quad Core processor … wdtv’s are single core 700 mhz with 512mb of ddr2 ram)