Yes, there is the risk that people who are unaware of any sort of voter registration requirement are less likely to show up to vote. That doesn't just apply to voter identification, although certainly if there's a new law, if you're adding additional identification requirements, one of the big concerns would be that someone who has voted in the past but really doesn't pay attention to politics much in between elections, may not be aware of changes in the law and may show up to vote like they normally would every year, or whatever time period, and not be prepared to participate in the election with their identification. I think you're right that this is a risk of these sorts of identification laws.
That risk is mitigated over time as people become more and more aware. I think, on the second point you asked about, education is absolutely critical in informing voters and letting them know about the new requirements, explaining how they go about securing the proper identification that they need on election day.