In the rapid evolution of digital marketing strategies, Influencer Ad Agencies have emerged as a highly influential player. These are platforms that facilitate alliances between brands and social media personalities, known as influencers, that possess significant clout in their respective domains. The novelty of such agencies resides in their ability to tap into the trust and credibility built by influencers among their audience, enhancing the impact of brand messages.

As it stands, the landscape of Influencer Ad Agencies is set to undergo seismic shifts, driven by several emerging trends and predicted transformations. This discourse will delve into these forthcoming changes, underpinning the relevance of each trend based on industry insights and its implications on the future of these agencies.

The first prophecy concerns the democratization of influencer marketing. Following the Pareto Principle or the 80/20 rule, traditionally, a small percentage of influencers with enormous followings have been commanding a significant proportion of brand collaborations. However, this is set to change, with more brands venturing into the 'long tail' of influencer marketing, harnessing micro-influencers and nano-influencers. These individuals, though possessing fewer followers, boast higher engagement rates and a more genuine, personal connection with their audience. Hence, their potential for impact is substantial.

Given this trend, Influencer Ad Agencies will need to rethink their strategies, placing more emphasis on the quality of interactions rather than quantity. This will necessitate a more nuanced understanding of these smaller influencers’ audiences, their interests, and engagement patterns. Furthermore, transaction costs may rise with the increase in partnerships, requiring agencies to devise efficient operational workflows.

Secondly, the rise of new social media platforms will reshape the influencer landscape. The emergence of platforms like TikTok, Clubhouse and the resurgence of platforms like Snapchat, present new opportunities and challenges for Influencer Ad Agencies. These platforms typically attract diverse demographics and foster unique content consumption habits. Consequently, agencies will need to be adept at adapting their strategies to these platforms, understanding their algorithms, and leveraging their unique features for maximum impact.

The third prediction revolves around the growing importance of data analytics. As influencer marketing matures, there will be an increasing demand for sophisticated data-driven insights. These insights will serve to quantify the ROI of influencer collaborations, provide predictive models for future campaigns, and essentially, offer a more granular understanding of consumer behavior. Agencies, hence, need to invest in robust data analytics capabilities, allowing them to offer brands more precise targeting, enhanced campaign planning, and comprehensive performance evaluations.

Last but not least, as per the Coase Theorem, originally elucidated in the realm of law and economics, we anticipate a shift in the organizational structure of Influencer Ad Agencies. As transaction costs decrease due to advancements in technology and better access to information, there may be an inclination towards decentralization. This trend could possibly stimulate the creation of more specialized boutique agencies that cater to niche markets, thereby promoting a more personalized and targeted approach to influencer marketing.

In conclusion, the future of Influencer Ad Agencies is multifaceted, and navigating this terrain will require agility, innovation, and a deep understanding of the evolving digital landscape. As the power balance in the social media realm continues to shift, it will be interesting to see how these agencies adapt and evolve, shaping and being shaped by the zeitgeist of our digital age.