I'm loving my Stylo, but I'm not holding my breath for Marshmallow. Nexuses will get it in the Fall and we might see it in Spring . LG will make the G4 and G3 a priority before the Stylo.
Actually G4 is this week and G3 is next week. the Stylo is so close to the G3 that they will be able to roll us out within a week of that model. LG is not kidding around on these updates, especially with their flagship 64 bit Stylus enable phone that is selling out everywhere.