You need i90 to access Heavensward due to it being a requirement for the Steps of Faith trial, though the majority of players will be i130. I imagine to some extent this may trivialise the early dungeons for better geared players, but then that's really nothing new for most of us as every dungeon released since 2.0 launched has been balanced for 20-30 iLvls below the current cap... Having said that the Steps of Faith was actually very over-tuned for its i90 requirement so SE may be rethinking how they balance content.

Most MMOs offer under-geared players a means of rapidly catching up through the early quest rewards in the expansion. What form that might take here though, and at what level the current i130 gear becomes obsolete remains to be seen.