At least 11 companies, including Zynga, have tools from Nintendo to make 4K Switch games. [...]

Employees at 11 game companies said their teams were in possession of Nintendo’s 4K development kit for the Switch. The companies span the globe, ranging from large publishers to small studios and include at least one that has never made a console game before, Zynga Inc., according to the employees, who asked not to be identified because they weren’t authorized to discuss their projects publicly. [...]

But a system capable of handling 4K games isn’t expected to be released until late next year at the earliest, people familiar with the plans said. [...]
Nintendo Switch 4K: Developers Make Games for Nonexistent Console - Bloomberg