finetuning the lemonade stand analogy, both stands would need to be the same price, as the busy street has a sale price restriction for alternative stands. The lemonade vendor would need to decide whether it was worth losing the busy street as a whole in order to use the dark alley in order to keep the lower 1$ price
Developers and studios would need to be willing to leave steam (whos market share is estimated to be 75-80% of the PC third party gaming market) and either make their own(costs money + no userbase) or go to the next big thing which would likely be epic (who is at an appoximate 15% game share despite having a 12% cut vs 30 and releasing weekly free games)
My money is on the devs just raising their price to match steams new price and also allowing both markets to exist.
note: The percentages I gave are actually on the lower end by the way from the numbers I found. I saw some sites quoting steam to be in the 90's for market share in third party PC gaming.