In spite of the Google Pixel 2 and 2 XL only having recently been announced, it is now being suggested that the codenames for the 2018 Pixel lineup are Albacore, Blueline and Crosshatch. At present, the details are quite light and due to the very early arrival of these codenames, they are subject to change, or being wrong. However, the details on these new codenames come from a report out of Droid Life which in turn credits a 'trusted source' with the information.
What is interesting about these codenames is their seemingly alphabetically nature. Which is also something the report states is how Google may refer to them going forward. According to the details, by adopting an ABC naming scheme Google is hoping to better keep their identities under wraps. In either case, of the three suggestions it does seem as though crosshatch is currently the most likely to be correct as Droid Life has picked up on a Pixel-related AOSP listing (shown below) which has gained a new comment today. A comment which does indeed mention the crosshatch name. Although as the current report also points out, that same listing does also reference a 'wahoo' device. This is another name that is not currently associated with a known device and the details on this are even more limited (and somewhat contradictory) than those suggested for the other three names.
As for the actual devices, and as to be expected, next to nothing is actually known about them. By definition, the details here suggest that there will be three devices arriving although this is something that should not be taken for granted. Prior to the release of the current (2017) Google Pixel line it was believed there would be three Pixel phones released this year and much of the speculation on this was due to three codenames having come to light. However when it came to the launch only two were announced. So there is history to suggest the same thing could happen again next year. In the meantime though the details suggest there will be three. What may be of additional interest is the latest information does go on to note that while two of the codenames refer to premium devices, one of them (no mention of which one) refers to a high-end device, but not necessarily a premium one. While that distinction is a difficult one to make, it is possible that it relates more to the pricing structure that might be in place next year.