Ever since the Switch was unveiled, people have been speculating that the system’s dock may include additional hardware that supplements the main tablet and makes the system more powerful when it is docked- a bit like the Surface Book Microsoft has with the discrete GPU. However, Nintendo have categorically denied such a thing.
It turns out they were both right- Nintendo was right in that the dock has no additional hardware to help Switch games run better, but people hoping for the dock to enable Switch games to run better were also right because of sheer physics. Laura Kate of LPVG is reporting that because the system’s dock uses USB-C connections, which are high speed USB 3.0 compliant, when the system is docked, components will run at a higher clock speed to facilitate 1080p resolutions on the TV. Both video and power will be transferred over USB-C when docked, which will also help with this. Additionally, an extra fan in the dock will dissipate the heat generated by the higher clock speeds.
So yes, there will be a boost- just not of the nature that many possibly expected. Personally, I cannot wait for January 12, which is when the Switch event will be held, to come about so we can get final, concrete details and information on the system once and for all.