The option to tax, when made, is irrevocable for 20 years, so the first options will be capable of being revoked in 2009. For owners of certain types of property, there may be an advantage in revoking the election, in which case VAT charged for work done to repair and maintain the property will only be recoverable until the election is revoked.
In particular, if the sale of the property to an organisation which cannot recover the VAT charged is likely, removal of the option to tax should result in a better sale price, since the irrecoverable VAT otherwise charged represents an extra cost to the purchaser.
The decision as to whether to retain or revoke the option to tax should not be made without professional advice. If you opted in 1989 to tax a building which you still own, the time for thinking through the implications is now.