From pubmedcentral
: "And, intriguingly, mitochondrial DNA has now been extracted from Quaternary fossil teeth, allowing fossil samples to be placed in the same population genetic framework as extant populations living in the same geographic area"
The above case is only 2,400 years old. They have Neanderthal DNA much older than that.
But I think 2 million years will be a challenge for a while to come for DNA studies.
Thanks Doc