1) People who sell re-filled cartridges, and offer to refill your existing cartridges will no longer suffer malicious lawsuits from HP & Lexmark.
2) That will increase the supply and create a price competition between re-fillers. Making it possible to easily find ink cartridges at 1/2 to 1/3 the price that the printer manufacturer sells it for.
3) The manufacturers will reduce prices on their ink cartridges in order to support their revenue stream.
I also expect more counter measures like ink cartridge chips that 'self destruct' when the cartridge is exhausted to prevent refilling. And aggressive prosecuting under the DMCA people who reverse engineer cartridge chips to create work alike versions.