According to the Egami Blog, Canon has filed an optical design patent for an EF 24-105mm f/4 lens. While the patent does not specifically mention the "L" branding or "IS," the current 24-105L is more than a decade old and may be due for a refresh in the not-so-distant future.
That said, the Canon EF 24-105mm f/4L IS USM is a lens I use very frequently, and right now you can get a Canon USA refurbished model for only $599.99 + tax & shipping.
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