I'm only basing my post on what's been presented in the media. It does appear that the knife was one of the crucial piece of evidence. I don't know what else they have without a total redo of the first trial in which they were both acquitted based on not enough evidence. I guess I expected this would've been a bombshell but it turned out to be a flop.
All three suspect were convicted of murder. That means that Sollecito and Knox were convicted of murder. They appealed this conviction, but there were serious irregularities in the hearing and the decision was annulled so ... we have Appeal: Take 2.
The first annulled appeal concluded that there was no DNA on the knife. We know that isn't true, so there is no question that there were serious errors in the DNA analysis.