If you have the entire sequence of an individual's genome, all other tests for specific mutations or polymorphisms in their germline DNA can then be eliminated.
The next "level" would be sequencing tumors. However since tumors can be genetically heterogeneous, you would need some quantitative methods to look for the distributions of mutations within a tumor.
Lastly, I would think the informatics to manipulate the linear sequence information might exceed in cost the the cost of doing the sequencing. Some sophisticated software programs cost thousands of dollars or more.
William E. Winter, MD