So, not to be a jealous 550D user, but is there any possibility of the HD-zoom feature to come to the 550D?
As far as I've read so far, they both have the same processor and same sensor so could it be as simple as a software update?
to be frank: really really unlikely. you paid for a product when you bought it, and you got the product you expected, as advertised. there's no obligation for canon to retroactively make your previous purchase better.
yes, I know they did make some monumental firmware updates to the 5D Mark II ... but, being frank again here, that was a banner-carrying camera for them ... and the low margin, continuously updating rebel lineup doesn't command that same level of do-it-or-die respect from inside or outside the company