I cannot believe that it is a serious suggestion to run a cable to a WiFi AP/Repeater/Extender in order to network a fixed device. That sounds absurd to me.
Anyway, I get the point. Everything is moving to WiFi. Most of the alternatives to OpenSprinkler are WiFi-only so I can see that is what customers (on the whole) want. I did see OpenSprinkler having an ethernet port as a point of difference – a competitive advantage, but it has other advantages too.
I have bought the OpenSprinkler 3.0 now.