Speculation from one of Nintendo's hardware partners:
The new “mini” Nintendo Switch will take advantage of a two generations of die shrinks to its Nvidia Tegra processor to deliver 1080p mobile gaming to a broader audience. By joining the joycons to the main body of the Switch, Nintendo will squeeze out the expensive and sophisticated wireless joycons and create a mobile-first Switch platform. The die shrink of the Nvidia Tegra processor will provide better battery life and a meaningful upgrade to a 1080p display and graphics in mobile mode. The new mini Switch, and an upgraded standard Switch are poised to address a broader market and capitalize on their growing software and user base.