Clues on Google issue tracker point to LG-made, Google-branded device being in the works.
The codename "Taimen" has cropped up a few times over the past few months, apparently in reference to a new big-screened Google device — presumably carrying the premium Pixel branding. Droid-Life first reported the name back in March, with claims it was a "separate project" within Google. The company uses various species of aquatic life as codenames for its phones and tablets, so Taimen, one of the largest salmonids in the world, fits the bill for something with a larger display.
Geekbench results point to a Snapdragon 835 and 4GB of RAM, but not much else is known for a fact — including whether Taimen is a phone or a tablet. The few scattered references to Taimen in AOSP (Android Open-Source Project) commits don't do much beyond confirming Taimen's existence as a Google Android product with Snapdragon 835.
With recent rumors suggesting the larger of the two HTC-built Pixels has been canceled, speculation around Taimen has ramped up. It's unlikely Google would release just a single small Pixel phone, so common sense would suggest that Taimen will take the place of Muskie, the canceled second-gen HTC Pixel XL, as the this year's plus-sized Pixel. (For what it's worth, GFXBench results suggest a 5.6-inch 2:1 display for the smaller 2017 Pixel, so expect something north of that for Taimen.)
About as close as you're going to get to a smoking gun, identifying LG as Taimen's manufacturer.
Anyway, back to the LG connection. For that, we have the eagle-eyed folks at 9to5Google to thank. They spotted a bug report (apparently erroneously) posted to the public Android issue tracker by an LG employee; a reply to the issue report by a Googler asks that it be re-filed under "Android > Partner > External > LGE > Taimen > power."
That's about as close as you're going to get to a smoking gun, identifying LG as Taimen's manufacturer.
If true, the move could help buoy LG's mobile division as it pushes back towards protifability — a few million Pixel phones sold won't move the needle significantly for LG, but it certainly won't hurt. It'll also reinforce the longstanding hardware partnership between LG and Google, as Taimen would emerge as the fourth Google-branded LG phone. Unlike the Nexus 4, 5 and 5X, the upcoming Pixel device probably won't bear any LG branding.
LG Display — a separate company in which LG Electronics is the largest stakeholder — is also reported to be producing curved OLED panels for at least one of the 2017 Pixels, with Google being prepared to offer an investment of at least $880 million to sweeten the deal.
At the very least, we'd expect an LG-made Pixel to source its OLED screens from LG Display. In the context of a possible Google investment, and the continuing global OLED shortage, the use of an LG panel in both would make a lot of sense.
Don't expect the two 2017 Pixel phones to look exactly alike.
As for HTC, the probable cancellation of Muskie in favor of the LG-made Taimen isn't great news. AC understands that the HTC/Pixel deal was intended to run for multiple years, and may still do. Either way, the Taiwanese company surely isn't thrilled to have to share more of the limelight — and more importantly, profits — with LG.
For consumers, what this means is you're likely to get a 5.6-inch 2017 Pixel made by HTC, with 2:1 (-ish) aspect-ratio display — and a significantly larger Pixel made by LG. It'd make sense for the two to share the same aspect ratio and specs — and thus far the leaks point to both devices sharing a Snapdragon 835 platform and 4GB of RAM. But given that we're dealing with two different ODMs (original device manufacturers) this year, we should be prepared for some external hardware differences. Don't expect Taimen and Walleye, the smaller 2017 Pixel, to look exactly alike, even though Google might do everything it can to emphasize common design characteristics.
Made in Korea vs. Made in Taiwan.
We'll have to wait and see whether the use of two different manufacturers helps or hinders Google's ability to get Pixels on store shelves this year. The company has notoriously struggled to meet demand for the current Pixel and Pixel XL over the past eight months, and the new Google hardware division is surely hard at work looking to avoid any such issues with its second round of phones.