For one thing, Microsoft might be working on an AMD-powered Surface Laptop. This wouldn't be surprising given that AMD has made big strides with its Ryzen processors, and the new Laptop would be based on the Picasso architecture.
The AMD-based Surface Laptop is slated for the fourth quarter of 2019, as is a redesigned Surface Pro. This will be the first major redesign of the tablet since the Surface Pro 3, and it's been rumored for some time.
But another, more substantial hardware release for Microsoft could be Andromeda, which according to the book, is now slated for late 2019 as well. Unfortunately, it's not the pocketable LTE device that many had dreamed of though, at least for the time being. It's larger than what was initially rumored, and that original device has been scrapped for the time being.
On to 2020, Microsoft will be bringing the modular concept that it is using with the Surface Hub 2 to the Surface Studio. That means that the next Surface Studio could be the Surface monitor that many have been asking for. This is a huge shift for the all-in-one PC, which isn't very upgradeable at all in its current form.
And of course, there's Surface Book. According to Sams, this isn't slated to be refreshed until the first quarter of 2019, but for good reason. Microsoft is working on a new hinge design, so it seems likely that the infamous gap will finally be gone.