It would have been quite a big deal for Sony to market the Xperia Z3+ as the Z4 outside Japan. The single-digit move from Z3 to Z4 should suggest a tangible upgrade over the previous flagship. Given the near identical design, Sony sensibly decided to stick with a name that tied the Z3+ as a premium offering for the Z3 series.
When Sony was working on the Z3+ there is no doubt it was intended to be the next true flagship device. The internal codename for the device “i1-iv” suggests as much i.e. this is the fourth iteration from Sony’s ‘One Sony’ philosophy that started with the Xperia Z1 (i1). However, a lot can happen between the drawing board and getting a product to market, especially against strong competitor offerings, hence the more modest “Z3+” tag.
Interestingly, Sony felt that the Japanese market is not so synchronised with the global market in this regard. The Japanese carriers view of the Xperia Z4/Z3+ was that it offered a substantial upgrade over the Z3. Upgrades include a new Snapdragon 810 chipset, capless USB port, faster LTE support all wrapped up in a lighter, smaller offering.
Therefore, Sony Japan decided to market it as the Xperia Z4. Obviously this could confuse what happens in the next flagship release after this one. However, Sony confirmed that the next flagship model will not use the ‘Z4’ tag. Logically, if Sony were to release a ‘true’ flagship successor in the second half of this year, there is a strong chance it would be named the Xperia Z5. Or Sony may move away from the Xperia Z series naming altogether, time will tell.
Sony Mobile statement on Xperia Z4/Z3+ name change
“The main reason for the name difference here (UK) is down to Sony being such a dominant force in the Japanese market [where] consumers crave flagship devices with the latest features as soon as they can be delivered. Xperia Z3 continues to perform well as our flagship device across the rest of the world. To address those customers that would like to have the very latest features and refinements, we have introduced Xperia Z3+ as a premium addition to our existing flagship Z3 series.”