Which serial killer do you believe can be traced back to by DNA and forensic evidence in the modern day?
As I understand it, there is one I most suspect we'll see breakthroughs on in the next few years, being the I-70 Killer. From his identification at the Terre Haute liquor store murder in 2001 to casings found at each of his killings, a quarter of a century is not that strained of a stretch to assume preserved DNA evidence won't link together with an analysis of familial DNA as was the case for the Golden State Killer, Joseph James DeAngelo.
One I believe we may never know about is the Zodiac. 25 to 30 years is feasible in the case of the I-70 Killer, but the Zodiac has spent 58 years since his last confirmed murder in 1969 in relative silence from the many he committed in the 60s. If there is something led up to in the case after a half-century of speculation, it would end at a grave. At the least, that would be closure for the case.