In theory it is possible but I don't think governments are going to allow that unless they can control them. When you buy a house or a house or a car, you go to a notary or a lawyer who has a government license, who pays taxes and who will charge you taxes for the transactions. Unless they keep getting the same taxes, I don't think they are going to legally allow smart contracts. Apart from that, lawyers and notarys are going to complain if they are out of business but I hope technology beats them.