GP needs to avoid attack speed like the plague, there is nothing in his kit that benefits from attack speed, no on 3 hits, no ranged auto attacks, nothing. Triforce is now spending more gold on its attack speed, becoming a bit less efficient.
GP also needs crit, Tri will have less crit. GP has to build tri tho because his entire kit is based around proccing 200% dmg sheens, so now his whole kit based around crits and sheen procs will not have a smooth item path, as he will be forced to buy a pure attack speed and crit item in a zeal to make an IE ever make use of its passive effect.
Over all GP is in an ok spot atm, so he will just fall down to being one of the many 'kinda bad' champs, which LoL has a ton of, so its not all that big of a deal. He will prob get something good for him in like 6 - 12 months and be in an ok spot again. With this change though, Jax and Irelia get to come back to being in an ok spot now instead of being 'kinda bad'. The cycle of LoL continues on and on!