Thunderbolt 3 has been the fastest and most functional port for years, but a new generation is on the horizon. Configured to compete directly with the impending USB4, it is likely that Thunderbolt 4 is not "so" different from Thunderbolt 3, but it may have some new features that make it the port of choice for those who want high-speed transfers and device connectivity in the future.
Intel officially announced Thunderbolt 4 at CES 2020. Declaring that Thunderbolt 4 will be backed by its next Tiger Lake mobile processors, scheduled to debut sometime in 2020, probably the second half. And in this way join other technological improvements such as the native support of Wi-Fi 6 and Bluetooth 5.
Although laptops with Tiger Lake processors will debut later in 2020, it can take several months for them to become commonplace. 2021 see a much wider variety of options for potential buyers interested in the capabilities of Thunderbolt 4.
As for speed, it is likely that Thunderbolt 4 does not work faster than Thunderbolt 3. That is somewhat surprising, since speed has been one of the main advantages of Thunderbolt 3, with its maximum capacity of 40 Gbps. In contrast, USB 3.2 2 2, the fastest specification of USB ports at the time of writing, is 20 Gbps. First, Thunderbolt 4 was expected to improve that, with Intel claiming it will be four times faster than USB, which led many to expect 80 Gbps bandwidth for Thunderbolt 4.
Intel then clarifies that it will be four times faster than USB 3.2 Gen 2, which has a maximum speed of 10 Gbps. Thunderbolt 4 should work at a maximum performance of 40 Gbps.
Thunderbolt is a standard full of features, from enabling external graphics cards to providing access to the Ethernet network. At CES 2020, Sarah Kane of Intel said that Thunderbolt 4 "standardizes the PC platform requirements and adds the latest Thunderbolt innovations," but did not go into details about what those new innovations were.
With some suggestion that USB4 incorporate Thunderbolt 3 capabilities into its standard, making the cables interchangeable, it is possible that Thunderbolt 4 aligns more with USB4 to make it more of a conventional technology. If you cannot stand out in speed, you will have to do something quite special to remain relevant with the possible ubiquity of USB-C at USB4 speeds.
As more details about Tiger Lake come to light, we are likely to hear much more about what Thunderbolt 4 brings to the table.