My personal opinion is that this is very unlikely from Orange. The only option may be a hacked ROM from 'unofficial' sources.
As the mobile operators have to pay to license the OS, then develop compatible Ext ROM applications, they are more likely to simply point existing users at newer models and tell you to wait to upgrade (not much use if, like me, you are 1 month into an 18 month contract

)
O2, who have been longest in the Phone Edition market have never offered an OS version update, though T-Mobile are rumoured to be planning a WM6 update on the Ameo in some markets, though this is likely to be a chargable option.