When fossilization occurs, the organic tissue from the animals bone are replaced with minerals. Because of this, the cells are destroyed which means that the DNA is destroyed. This would make cloning a dinosaur from fossils virtually impossible.
Paleontologists have found soft tissue in the bones of a Tyrannosaurus Rex. Until this was discovered, it was thought that all soft tissue was destroyed in the fossilization process. Unfortunately, they have not been able to extract any DNA from the tissue.
There are many technological advances that are being discovered, but it is still unlikely that there will by any major breakthroughs in the cloning of dinosaurs, especially in our lifetimes.