The RIRs, which are the entities in charge of delivering addressing, do not have an estimate for how long everyone will use IPv6, but we can see the statistics worldwide in the following link: 

https://www.google.com/intl/es/ipv6/statistics.html#tab=ipv6-adoption

The complete transition from IPv4 to IPv6 has been a topic of discussion in the information technology community for many years. The exact estimate of when companies will go IPv6-only is difficult to determine due to several factors. Below are some of these factors and considerations that influence the pace of IPv6 adoption:

Factors influencing the transition to IPv6

1. IPv4 Address Shortage: The main motivation for the transition to IPv6 is the shortage of available IPv4 addresses. Although this drives IPv6 adoption, the reuse and sale of IPv4 addresses have provided temporary relief to the shortage.
2. Compatibility and Coexistence: The need to maintain compatibility with IPv4-only systems and devices has led to coexistence solutions such as IPv6 over IPv4 tunneling and network address translation (NAT), allowing for a more gradual transition.
3. Infrastructure Investment: IPv6 adoption requires investment in infrastructure upgrades to support the new protocol. This includes hardware, software and staff training.
4. Awareness and Education: Lack of awareness of the benefits and need for IPv6, as well as the training required to implement it, are significant barriers to its adoption.

Projections and Trends

• Continued Growth of IPv6: IPv6 adoption has been growing steadily, driven in part by Internet service providers, mobile network operators, and large enterprises that see the long-term benefits of IPv6 adoption.
• Regional Variety: IPv6 adoption varies significantly by region, with some countries and regions advancing faster than others due to government policies, infrastructure initiatives, and resource availability.

Conclusion

It is difficult to predict exactly when companies will exclusively use IPv6, as it depends on multiple variables, including technological advances, regulatory policies and market economics.

However, the trend is clear towards a gradual increase in IPv6 adoption. We could talk about a process that will extend over several years, even decades, before IPv6 becomes the universal standard, with the long-term goal of it eventually completely replacing IPv4.

The transition is more of a marathon than a sprint, with many companies and networks operating in a dual-stack (IPv4 and IPv6) environment during the interim period.