Does a minor software update effect rooting method?
This ultimately depends on the manufacturer. Samsung is not at all friendly to the rooting of it's stock ROMs, and does lots of modification to it's Android ROMs, so I'd say it is a real possibility. If it were me, I would install Cynaogenmod instead if I were to root but still wanted OTA updates.

Google itself, which is where the baseline Android comes from, usually doesn't care all that much if people want to root their devices, and usually doesn't plug holes that allow rooting unless customer data is at risk as a result.