That's indeed a big if, but even if it ends up being cheaper to use solar for most applications I can imagine fusion power would be a nice thing to have locally around major production centres where the power demand is much higher.

Solar is great for decentralized grids where one's neighbour basically buys excess power from you, but transferring gigawatts of power from a large amount of solar panels to something like a major industrial area /might/ be trickier.