Not really. The vertex shader only has access to individual vertices with limited to no knowledge of the whole mesh. Usually for terrains you would use a heightmap (a grayscale texture with black or white areas that define the shape of the terrain). You can use one big texture and then have the vertex shader only read the section that is relevant. You can do this with uniform variables, like a vector that defines a square region to sample the texture from. You can also alter the vertices randomly, like with perlin noise or other such functions.
