There is simply no way Serbian army would ever cross the border or fire any missile. Its just a show for their people.
As for local Serbs on Kosovo, they are doing the same mistake they did in other Ex Yu countries. Instead of accepting the country they live in, they set up barricades and allow themselves to be puppets of Belgrade's regime, which uses them to score few points among radicals. It can only lead to another exhodus for them if they continue.