This is a speculation post. As such it is subject to the vagaries of herd behaviour.
The single biggest change for me, is the player owned customs offices.
When bashing a customs office, you can achieve a lot given time and a t1 AFK fit glass cannon battleship or 2. I understand that concord will not intervene, but really hope that players are given a suspect flag while shooting one.
I confess to a 'rent seeking' desire; that is, to complain about how the evils of highsec player owned customs offices will destroy wormhole/null/lowsec customs office ownership.
But it won't; not significantly. Those doing extraction based PI will still suffer huge penalties in highsec; those wanting better returns in exchange for potentially higher risk will still seek out lowsec, null or wormholes.
There probably will be a difference in factory planets. I can see many barren planets being set up as P4 factories, with 0% tax.
I see many small industrialists doing so; then enjoying the attention of the bigger players, especially with planets close to trade hubs.
I have noticed already a large spike in certain P4 (advanced commodities) used in the construction of customs offices. My personal speculation is that this will continue until after the expansion drops and the rush to build customs offices is over.
Long term, I do see a probable fall in both the P3/P4 prices, as more players do highsec import based manufacture on low/no tax planets.
I also see a probable fall in lower priced PI commodities (Biofuels, Bacteria); as these are often lower bound by the highsec PI tax rate.
I think that the rest of the materials will remain largely as is, especially supply limited items.
There may also be a move away from single planet PI and towards multi planet PI as more players get access to reasonably taxed customs offices; I am unsure if this is enough to counteract a resurgent interest in PI long term.