They will not be making major changes to ARR or to HW. This should be clear with their stated intention to bring PTW to the game via the "jump potions".

Anything built with "PS3 Limitations" in mind will remain pretty much as-is as long as the game lasts. They simply won't have to factor in "PS3 Limitations" for future expansions. Now, it will be alternating "Toaster PC Limitations" then after they get rid of the Toasters, it will be "PS4 Limitations".

And they are killing the PS3 client COMPLETELY. If anyone is still on PS3, they need to upgrade to PS4 or PC before Stormblood hits, or they will be giving up the game entirely.