Big Data typically has low density data. By that, the volume of data is so large that the key pieces of valuable info is sparsely populated. It's up to having a good data person to search the data to find the nuggets of insight in the giant haystack.
Similarly, you can have Small Data that has high density of data, where the volume is less, with potentially higher nuggets of insight.
So just because you decide to move to Big Data, don't assume that your Small Data is obsolete.
There is still value there as well.