Sony may have let the latest in its line of Android flagship phones -- the Sony Xperia Z4 -- quietly slip into public consciousness by updating its Japanese website with a list of specs and features for the smartphone, but followers of the now nearly cult-status Xperia Z line in the U.S. certainly took notice.

The biggest question remaining for U.S. customers is when, or less-optimistically, whether, the Xperia Z4 will hit U.S. shores. According to CNET, which parsed through the Japanese-language listing for the phone, Sony's home-country release date for the successor to the Xperia Z3 is mid-year, and possibly later this quarter.

But there are no indications of an international launch date for the device yet, and the U.S. Sony Mobile page only lists the Xperia Z4 Tablet, with the smartphone to be found nowhere, under its "coming soon" banner.

This year's follow-up to the Xperia Z3, Sony's Xperia Z4 features a lot of the same hardware as the previous year's model, along with the same boxy (to some, awkwardly so) chassis and nearly identical dimensions -- except that the 2015 flagship is .4 mm slimmer than the Z3 and about a quarter of an ounce lighter.

The same 5.2-inch screen, with the same screen-to-body ratio, comes with the yearly update, along with the same decent -- if no longer particularly competitive -- 1080p HD resolution. Also the same: Sony's 20.7-megapixel camera which, though unchanged, will fare nicely against its Android competitors from this year. So will its front-facing shooter, which has been updated to 5.1-megapixels from the Z3's 2.2-megapixel selfie camera.

Inside, is this year's Qualcomm Snapdragon 810 quad-core processor, supported by 3GB of RAM. The standard model comes with 32GB of storage, with an option for 64GB, along with microSD support for up to 128GB expansion.

Of course, the flagship phone is built with Sony's well-known tradition of high water and dust resistance, coming with an IP6X dustproof certification and IPX5 and IPX8 certifications -- which basically means the Xperia Z4 is waterproof (to reasonable depth standards).

A nice little tweak -- among the dearth of significant updates in the new Xperia Z4 -- is a waterproof USB port, eliminating those pesky caps previous Xperia flagships needed sealed tight in order not to ruin your phone.

If this all seems particularly underwhelming -- even more so than HTC's tepid update this year of the 2014 HTC One M8 -- you're not alone. It's hard to see why Sony would want to try to compete in international markets against offerings like the Samsung Galaxy S6.

Nevertheless, for Sony fans, there's one glimmer of hope that the Xperia Z4 could eventually make its way to the U.S. market. According to UberGizmo, T-Mobile resumed its carriage of the Xperia Z3, after a just a couple-week retail stoppage. And it's back on the carrier's shelves at a big price reduction -- from about $630 off-contract to $500.

Could T-Mobile be resuming sales to clear Xperia Z3 inventory to eventually make room for this year's Sony flagship?

Who cares? At the current price -- and with the Z3 and Z4 being nearly identical -- Sony fans might as well buy Sony's 2014 flagship Xperia Z3 at a fraction of the likely price for the new one.