The technology probably does support it they just dont want to give you so much upload speed. Probably to stop people like me doing what I do, running servers.
Yes my site is fine on 20kb/s (actually ive limited it to 10kb/s) but the more the better. I intend to have downloads on my site. 20kb/s is very slow compared to todays internet speeds.
Cable is capable of speeds in excess of 10Mbps so if they can do it for download why not upload as well?
(Some stupid sod would probably turn around and say "turn the cable around and have upload not download"
)
As for 2Mbps, I meant when will 2Mbps customers be able to upgrade for free, not pay an extra £12.