Assuming travelling faster than light remains impossible. Theres the advantage that there are significantly less stars in the range of 0 to 100 lightyears than there are stars between 100 and 200 lightyears away. This means even if theres an alien civilisation, All the advanced ones must be far away and therefore our technosignature will never be exposed for XXXX years.
Our biggest signature/threat is that alien civilisations are receiving signals from our planet as it was thousands or millions of years ago and have send out a capable ship. But we still have the advantage of time. even travelling at near light speed, we might notice their technological attainment far before their ship can arrive. And thanks to einstein, the time dilation they experience at light speed means they dont have time to develop further during their travel. so an alien ship arriving is not game over as we have the space-time advantage. Therefore, military forces a few hundred years from now could be interested in defensive technosignature detection.