It is not possible to create raster images (GIF,JPG,PNG) of the desired size. Note, this is not a yEd shortcoming but a restriction of the underlying Java platform. (However, I bet you would be hard pressed to find any other application that can handle raster images of the desired size.)
I recommend exporting to SVG instead of a raster image format.
In theory, tiling would be an option for raster image formats. However, for that size you would have to use a lot of tiles. (E.g. even for huge 4000px by 2000px tiles, you would need 60 tiles per row and 90 tiles per column resulting in 5400 individual image files!)