Will help to buy be extended?

Not without permission. Help to Buy is designed to help people move on to or up the housing ladder, you should consider repaying part or all the Homes and Communities Agency’s contribution before making plans for improvements or alterations. This is because the Agency is trying to help future buyers and may use the proceeds of these repayments to make more assistance available. Therefore, consent will not usually be granted for significant home improvements. The Post Sales Help to Buy Agent will act reasonably in considering any application and will review cases of hardship if, for example, property modifications are required for a disability.
When your property is sold in the future, if improvements have been made with the approval of the Post Sales Help to Buy Agent, these will be ignored when your property is valued to work out how much should be repaid to the Agency.