[ ] update Fig 8 with DR5 comparison? --> depends on timescale of DR5
[x] In the introduction, when referring to a series of recent papers measuring chemistry and kinematic of the Galaxy. It could be appropriate to mention GCS (Nordstrom et al. 2004) which in fact has been the first stellar survey build on Hipparcos parallaxes (of course, now it's all gonna be wiped out by Gaia). Sure, if you have space besides Nordstrom you can also include the GCS version of Casagrande et al. 2011 ;)
[x] introduction, first paragraph, last sentence. Structure of the Galactic disk is specifically mentioned. Given the general terms you are discussing here, I would not focus on the disk only but any Galactic component. Maybe use a more general description such as "…as well as the study of stellar populations and Galactic structure" or something like that.
update Fig 8 with DR5 comparison?--> depends on timescale of DR5