Honestly, I don't think this will effect prices much.
There's also a gold sink coming with the release of Last Man Standing.
2500k in total is taken from players as an entry fee and 2000k is given back in rewards.
I can't see that affecting anything either, reason being there's still going to be a constant but ever-changing flow of money coming into the game.
If there's one thing we've learned from RS3, it's that gold prices only go down.