On the one hand, I would think that econophysics is off-topic. It is undertaken mostly by physicists, who publish their results in physics journals and it seems like Physics SE would be more appropriate. Most of the (academic) economists that I know, myself included, are somewhat skeptical of the entire undertaking.
On the other hand, one could have made essentially the same point about behavioural economics / psychology as recently as a decade or two ago, and that is now reasonably well-integrated into mainstream economics. To the extent that econophysics directly addresses questions about te dynamics of economic systems, it would seem to be on topic.