One is that walled gardens (platforms like Facebook, Google, Twitter, YouTube, etc. that attract loyal users and whose extensive audience data is coveted by and withheld from marketers) will open up their doors/data to marketers and advertisers. The other is that more and more walled gardens will pop up in the digital ecosystem as more companies take their cues from the success of the social and search giants.
The first scenario (lower walls) requires little more from marketers than what they’re already doing, and makes it much easier for brands to market across the various platforms.
The second scenario (more walls) would make advertisers have to choose more carefully where they want to go and what they want to accomplish in that space. Currently, advertisers are willing to put up with the stringent requirements that the platforms have for them because the audience data is of such good quality.
This reflects the actual complexity of the Internet markets, though, and forces brands to think beyond reach and scale to the intent of their would-be customers on a specific site or app. Since ad blocking became more of a problem, advertisers need to make nice with users and improve their content.
Walled gardens actually aid in that effort by requiring advertisers to fit/repurpose creatives to the specific style of the platform.
Barring any unforeseen market forces, (as in, if everyone stops using Facebook and Google) it’s dubious that walled gardens open themselves up beyond perhaps a modicum of transparency. But maybe that’s not such a bad thing if it brings better ads to users.