Sony Mobile seems to be running headlong into a nomenclature nightmare. With the excellent Sony Xperia Z3 awaiting a replacement, plenty of names, specs and other details have been bandied around.

With many expecting the Z3 replacement to be simply called the Z4, potential launch dates have been and gone: it wasn't at CES 2015, it wasn't at MWC 2015. That leaves Sony as the only big name that hasn't yet updated its flagship device. 

So what's the story? 

The Sony Xperia Z4 was announced in Japan on 20 April 2015. Many expected a global launch for Sony's new handset, but Sony has made it clear that the Xperia Z4 is for Japan and staying in Japan.

It's an incremental update over the Sony Xperia Z3, sticking to much the same design, but boosting the specs in some areas - mainly the chipset and the front-facing camera. It's a blink and you'll miss it difference.

Following the launch, we saw the Sony Xperia Z3+ name make it's first appearance. A Russian website reporting on the launch said of the international version (trans.): "…international market will be available to other device … with the highest probability, in late May. The name will be different … According to our information, the unit will be called Xperia Z3+."

That was the first occurrence of the Xperia Z3+ name, but it was quickly followed by another passing reference, this time in a Sony white paper, discussing compatibility of a cover: it listed Z4 and Z3+ as compatible.

Sony's white papers are issued for most devices it launches and hosted on its website for information. It's a legit Sony document, which we take as confirmation that the Xperia Z3+ name is real. Sony has since pulled that document.

We'd expect Sony to stick to the same OmniBalance design for the Z3+ as its been using for the past few generations of devices. The biggest clues to the changes come from recent launches - the Z4 and the M4 Aqua both retained waterproofing, but ditched the Micro-USB flap. 


We'd expect the contact charger from the side to be removed, making for a cleaner design, as seen in the two handsets mentioned above. Otherwise, we expect it to look very much like the Xperia Z3 as the Z4 does. The fact that Sony confirmed that a cover fitted both the Z4 and the Z3+ again tells us that the design will be the same.

The dimensions, therefore, would be: 146 x 72 x 6.9mm and the weight would be 144g, or pretty close to these numbers.

It's widely expected that the Sony Xperia Z3+ will have the same specs as the Xperia Z4.

That will amount to a 5.2-inch 1920 x 1080 pixel resolution display and you can expect plenty of talk about Triluminos, X-Reality and Live Colour LED technologies.

Displays aren't only about resolution - just look to the iPhone - but there have been rumours of a Quad HD display as well. There was a rumour from ePrice that two versions of the Z4 might appear - one at full HD, the other at Quad HD. Specifically, this rumour said that the higher resolution model would be launched in the USA. 

As we said, it's not only about resolution. The SGS6 looks fantastic, but that's down to colour and contrast rather than detail it can produce that you can't actually see. So if the Xperia Z3+ launches at full HD that's no bad thing. What's important is the quality of that display.

The Sony Xperia Z4 launched with a Qualcomm Snapdragon 810 chipset and 3GB of RAM. That's a logical step forward for the flagship Xperia in the Z3+, matching the move made by HTC with the One M9. 

It's 64-bit compatible, supporting Android 5 Lollipop, and has eight cores, designed to be more efficient and from the devices we’ve seen, plenty powerful. We can't see that Sony would opt for a different chip on the Xperia Z3+. 

We'd expect the 16GB model to be dropped in favour of a 32GB entry-level device, supported by microSD for storage expansion.

Of all the flagship devices out there, Sony often wins accolades for battery life. That's often achieved by careful battery management, as well as opting for a large capacity cell.

The Xperia Z4 has a 2930mAh battery and if it's the same bodywork on the Xperia Z3+, that would suggest the same size battery being in place. Sadly, that's a step down from the Xperia Z3 that rocked a 3100mAh cell. 

There was previously a rumour of a 3420mAh battery, but without leaving something out of the Z4 body, or being slightly fatter, we can't see how Sony would squeeze it in. Still, here's hoping.

With the Xperia Z's sealed body, it won't be user replaceable, but the range of controls offered by Sony's Stamina mode are really impressive, often the best in class. 

With the HTC One M9 being pretty average and the Samsung Galaxy S6 being a little weak, this could be where Sony really stakes its claim.

Of all the areas of Sony's next flagship, the camera will be the fiercest fight. With HTC stumbling with it's own 20-megapixel camera and Samsung universally impressing, Sony has to deliver on the camera. 

We'd expect Sony to add some tricks to the 20-megapixel rear camera, although it was fully-loaded and very capable on the Z3. 

We'd also expect a shift up to 5-megapixels for the front camera. This was the case for the Xperia Z4 and it makes sense of the Z3+. The selfie wars are still on us. 

The only date we have for the Z3+ is late May. With the launch of the Xperia Z4 in Japan effectively masking Sony's plans, there's little to suggest how the new handset will be launched. Sony might choose not to make a song and dance of it, and that might be reflected in the addition of a plus to name.

Are we expecting invites to a global launch event? Not really. There isn't a huge amount for Sony to say about the Xperia Z3+. It's incremental, but coming from a position of strength. There's a slight risk, however, as experience by HTC, that sticking to the same design might be seen as a little boring when set alongside Samsung's disruptive Galaxy S6 and S6 edge.

READ: Sony Xperia Z4 vs Sony Xperia X3: What's the difference?