older non HD receiver upgrade

[sbacchus]

my apologies if someone posted the answer to this already and i missed it (lot of new threads flying around!). has anyone been successful in upgrading an older non HD receiver (like a 4700) to a 211? i currently have a 921 (that i own) and two 4700s. i would like to keep the 921 and swap one of the older receivers for an MPEG-4 unit the general impression that i got before feb 1 was that this was not possible, but it seems like some stuff that was deemed not possible before is happening...