Not a day after the HTC Desire 728 made its debut in China, the Taiwanese mobile manufacturer is in the news again. This time, their pair of unreleased flagship devices are being thrust into the spotlight courtesy of HTC's new promotional ad for an upcoming press event later this month.

According to Chinese website ePrice with English translation from G for Games, the teaser hints that HTC will officially showcase not one but two flagship smartphones during a press event on Sept. 29.

The identity of the products has yet to be specified. However, it's safe to say that HTC will infuriate fans if not one of the devices turns out to be the much-anticipated HTC A9.

"The last time HTC teased a smartphone unveiling event, we assumed it would be for the much-rumored A9 (codenamed Aero), which is supposed to be the ailing Taiwanese manufacturer's next high-end offering. Instead, the 'big' reveal yesterday was the decidedly mid-range Desire 728. And so the A9 still isn't official," GSM Arena lamented.

To refresh the memory, the HTC A9 will have a six-inch display with 1440 x 2560 QHD resolution, a deca-core MediaTek Helio X20 chipset, 4GB of RAM and an IP certification. The flagship device will come in an all-metal build while employing a 2.5D curved glass design, Phone Arena earlier reported.

Fans can soon choose between a tyrant gold HTC A9 and a dark gray variant. The price range of the high-end device is rumored to be from $470 to $626.

With regards to the HTC Butterfly 3, a prior benchmark gave away the device's spec sheet.

According to a Compu Bench, the device will come with a 5.1-inch QHD touchscreen display, 3GB of RAM with 32GB of internal memory as well as Qualcomm's 1.9 GHz octa-core Snapdragon 810 processor with four Cortex-A57 high-performance cores and four Cortex-A53 power-saving ones.

The HTC Butterfly 3 will include a 20-megapixel main camera with LED flash and a 13-megapixel front-facing shooter. The device is said to run on the Android 5.0.2 straight out the box.

The next generation HTC Butterfly is expected to retail in Taiwan in October. The handset will retail for 20,900 TWD or roughly from €570 or $637, if current exchange rates stay the same, per GSM Arena.

The Taiwanese press predicts the HTC Butterfly 3 will most likely make its debut during the Sept. 29 event.

However, the same breath of certainty cannot be said of its debut partner. The Butterfly 3 might be paired with the HTC A9 or an improved M9+ with optical image stabilization and faster-focusing camera unit.