That's in addition to a feasible variant based on AMD. To date, if you wanted a Microsoft-made laptop larger than 13.5 inches, you had to buy a Surface Book 2.
But maybe you won't have to invest so much to get a big surface soon. The historically precise WinFuture argues that at its October 2nd case, Microsoft will reveal a 15-inch flavor of the next Surface Laptop (probably the Surface Laptop 3).
Most of the information are not accessible at this point, but it is reported that Microsoft intends to maintain the 3:2 display aspect ratio higher than usual as it did for the bigger Surface Book.
There may be more press gathering shake-ups. The Verge hopes an AMD-powered Surface Laptop 3 (the first AMD-based Surface of any kind) at the case, although it is uncertain whether the fresh chip choice would be accessible in the 15-inch scheme, the 13.5-inch or both.
The 2nd October introduction could feature a broad range of touch systems, including an enhanced Surface Pro, a Qualcomm Snapdragon-based scheme, and a dual-screen surface teaser. It wouldn't reflect Microsoft's radical exit (outside the teaser), but it would diversify a roster that is still quite tiny.