In the digital age, the business ecosystem is tightly entwined with a myriad of technological advancements. Among these, Application Programming Interfaces (APIs) have emerged as a fundamental pillar for establishing digital connectivity. They have become the DNA of digital ecosystems, enabling software applications to interact and share data and functionalities, thus creating a symbiotic relationship between various digital entities. The growth of API integration companies, the entities that facilitate such interactions, has subsequently been substantial. As we advance into the future, the paradigm of API integration companies is bound to metamorphose, influenced by various technological trends and market dynamics.

Firstly, we must understand what API integration entails. API integration is a link that allows two or more applications to communicate and share data and services. It is the glue that binds different software applications, enabling them to work symbiotically and provide more holistic and comprehensive services. API integration companies come in to facilitate this interoperability, helping businesses to streamline their processes and become more efficient.

The evolution and proliferation of Cloud technologies have been a significant driver of the growth of API integration companies. With businesses increasingly adopting Cloud-based solutions, the demand for 'Cloud-friendly' APIs has skyrocketed, creating a fertile ground for the expansion of API integration companies. These companies, in turn, are continually developing more sophisticated APIs to cater to the more complex Cloud-based applications, thereby feeding into this symbiotic relationship.

The future of API integration companies is set to be shaped by several emerging trends. One such trend is the rise of Artificial Intelligence (AI) and Machine Learning (ML). AI and ML are increasingly being integrated into APIs, with API integration companies developing 'intelligent APIs' that can learn from data patterns and improve their performance over time. This trend is set to continue, with intelligent APIs expected to become a staple in the digital ecosystem.

Furthermore, with the increasing concern over data security, the integration of blockchain technology into APIs is another trend to watch. Blockchain technology can provide a secure and transparent environment for data transactions, making it a viable solution for securing APIs. API integration companies are expected to invest heavily in blockchain technology, thereby driving its adoption in API integration.

Another emerging trend is the adoption of microservices architecture, which involves breaking down an application into a suite of small services, each running in its process. Microservices allow for more agile and scalable applications, making them increasingly popular among businesses. This trend is driving the demand for APIs that can facilitate communication between these microservices, thereby providing an opportunity for API integration companies.

From an economic perspective, the market for API integration companies is expected to grow exponentially. The increasing digitalization of businesses, driven by the need for efficient and streamlined operations, is fueling the demand for API integration. Furthermore, the rise of the 'API economy', characterized by the monetization of APIs, presents a lucrative opportunity for API integration companies.

However, this growth is not without its challenges. Regulatory issues, particularly around data privacy and security, are a major hurdle for API integration companies. Moreover, the rapid pace of technological advancements necessitates continuous innovation, placing a strain on resources.

In conclusion, the future of API integration companies is bright, albeit fraught with challenges. The rise of AI, ML, blockchain technology, and microservices present both opportunities and challenges for these companies. Nevertheless, with the right strategies and a keen eye for innovation, API integration companies are well poised to navigate this dynamic landscape, driving the digital transformation journey for businesses worldwide.