The temperature of steam is related to pressure. The greater the pressure, the higher the temperature that steam can reach. Therefore, in order to increase the temperature of steam, it is necessary to increase the steam pressure.
The heat transfer coefficient of steam is different under different pressures. If you only rely on external heating without increasing pressure, raising steam temperature will consume a lot of energy, and the theoretical heat exchange area is also large, just like you use circulating water to cool high-temperature gas.
However, if the pressure is to be increased, the boiler pressure should be increased accordingly, because there is no way to pressurize the steam, and it can only be controlled by the boiler. In this case, the problem goes back to the boiler, and it is simpler to pressurize and heat the steam directly on the boiler, which puts forward higher requirements for the boiler.
Therefore, heating the steam pipeline can theoretically increase the steam temperature a little, but the efficiency is very poor, which is almost impossible to realize in industry.