Agriculture will always be subsidised as its too important an industry for government not to have a hold over farmers.
Subsidies may be less but they will be at alevel where they are worth claiming and DEFRA can still have a hold over farmers,not to mention all the jobs within government which rely on a subsidy system.
I'm involved in a couple of things at government level. I am telling you, if you are a low-land farm in the heart of the south east and you do nothing for the environment, you are not open to the public then you will not receive subsidy.