In one sense the court left open challenges to Voter ID cases, but also placed emphasis on states to resolve election issues.
Two good case assessments from the SCOTUS blog note:
"The voter ID ruling may turn out to be a significant victory for Republicans at election time, since the requirement for proof of identification is likely to fall most heavily on voters long assumed to be identified with the Democrats — particularly, minority and poor voters. The GOP for years has been actively pursuing a campaign against what it calls “voter fraud,” and the Court’s ruling Monday appears to validate that effort, at least in part. The main opinion said states have a valid interest in preventing voting by those not entitled to do so, even if there is no specific proof of that kind of fraud in the state.
While the Court’s main opinion said it was “fair to infer that partisan considerations may have played a significant role” in enacting the photo ID law, it went on to say that that law was neutral in its application and was adequately supported by the justifications the state had offered."
"Democrats argued that voter impersonation is rare and that voter ID requirements, by making voting a more onerous task, actually tend to undermine public confidence in elections; Republicans submitted evidence that, they asserted, demonstrated the precise opposite. The Court made clear that such factual disputes should be decided by legislatures, not courts. The court exhibited the same hands-off attitude that it has exhibited toward redistricting disputes in recent years."
I'd expect more states to quickly adopt Voter ID laws, where challenges may be pushed forward on the local levels and appeals may bring the issue back to the Supreme Court further down the line.
As this post says, more challenges to such ID laws are almost being invited by the court:
"The lack of a majority opinion, moreover, injects some uncertainty into the appropriate standard for reviewing other challenges to onerous election laws. The Court’s specific split in this case will blunt charges that this is a politicized 5-4 decision — and it is significant that the Court, once again, has failed to cite to its opinion in Bush v. Gore."