In the most general way, the future of any wine depends on its inherent balance and structure. A wine that is out of balance when it is young will not become more balanced as it develops. In fact, imbalance always becomes more pronounced with time. On the other hand, speaking to the specific issue, if a wine is even searingly tannic in its youth (as happens not infrequently with, e.g., the wines of Bordeaux and Chateauneuf-du-Pape) but both balance and structure are to be noted, this is not an imbalance as much as it is a youthful expression and, especially considering the region, the varieties and the vintage year, one can often make good predictions for that balance becoming more visible and more "acceptable".
You may have noted in not a few of my tasting notes that I sometimes write "destined always to be a muscular wine", but then again that sometimes with the additional comment that muscularity and elegance can often walk hand in hand.
When tasting I am usually a swirler – that is to say, forcibly swirling the wine in my mouth with the lips pressed together tightly. When it comes to wines about which I have to wonder about whether the tannins and other elements will eventually come together, I am also a swisher – that is to say, taking the wine into the mouth, volubly sucking in some air and only then pursing the lips in order to swirl.
Also to be considered when tasting a wine in its youth is the overall "track record" of that wine from previous and similar vintages as well as the history of the wines from that winery.
I sometimes like to joke that there are three major factors involved in responding to a question such as this: "balance, balance and balance". Perhaps a humorous way of saying it, but quite true.