On one hand, yes, historians of the present in the future will need to update their methods - in fact, many already are. Digital preservation brings with it the possibility of creating digital tools to collate and analyse information in new ways, and many historians are actively involved in that process. Not everyone, for sure, and there are open questions as to how useful or insightful any given digital tool actually is, but on the whole that's a direction that the field is heading in.

But I disagree entirely with the idea that the wealth of documentation future historians will have (or any level of documentation really) can render historians obsolete through a perfect knowledge of the past. For one, we'd still need somebody to process the data - the whole point of a history book is that the author has collated all the information they could, decided what's important and communicated it to the reader in a clear way. Having more documents just makes this process more important. For another, especially given that digital records are massive and fragile, it seems unlikely that gaps won't exist, to say nothing of more human efforts to conceal and classify material they don't want to become public. More fundamentally though, the question contains a fundamental misunderstanding of what the purpose of historical research actually is. We aren't on a quest to discern the full and perfect truth of what exactly happened in the past, after which we can move on to the next mystery. Historians are generally much more concerned about interpreting and explaining the past, using what evidence we have to understand more abstract and subjective aspects of human existence. Even when historians agree on what happened in the past, we still tend to disagree on why it happened, and likely always will, because it is impossible to be entirely subjective in making such conclusions.

I'll use a rather banal analogy here to demonstrate why historical analysis will still be required in the future. Say that, for whatever reason, historians of the future are really super interesting in why local high schoolers Brad and Bradette broke up in the summer of 2019. Thanks to social media, we'd have an unprecedentedly detailed digital source base - we have photos, public status updates, private messages, emails. Yet I doubt it would be easy to analyse the relationship failure. As I'm sure you're aware, our social media personas don't always reflect reality - how far do their public updates actually reflect what they feel? Are they trying to project or perform a particular version of themselves - perhaps as blase and unconcerned about Bradette, or as publicly scorned and wronged? Even private messages are performative - just as letters were back when teenagers knew how to use pens. What if both sides told their friends different versions of events? What if Brad told different friends different details, knowing that Chad would be sympathetic to one version of events, but Ahad would view that version differently? We also need to acknowledge that there might simply not be a single true version of events - both Brad and Bradette could tell the unvarnished truth, but still give very different accounts of what happened. There's no objective way to sort out the tangled lives of Brad and Bradette - any historian who dealt with the question would need to come up with an explanation that accounted for the evidence as best they can, based on their own interpretations - as we do today.