We have talked about how Sony was expected to announce the Xperia Z4 smartphone at Mobile World Congress 2015. To this writing, this has not yet happened, and one has to wonder why is there a delay of the Z4 smartphone, not to mention the delay of the Android 5.0 update for the Xperia Z2 and Z3.

Here's what we know about the Sony Xperia Z4 tablet, according to Ubergizmo. It is a high-end 10-inch tablet with a 2K display, a first for any Sony tablet. It is powered by a Qualcomm Snapdragon 810 chip, with about 8 cores and an updated graphics unit for the best of Android games. The Z4 tablet has 6000 mAh of battery capacity, which is much less than the iPad Air 2, but can play video up to 17 hours on a single charge.

So when is the Z3 and Z2 going to get their Lollipop update? There doesn't seem to be any change since we last reported on it last month, with Sony's current flagship phone, Xperia Z3, being confirmed to get the Android 5.0 Lollipop OS update in February along with the slightly older Z2. The most recent source that I could find at The Christian Examiner on this topic also revealed that the download date is still uncertain.

A manual download is available for the Z2 and Z3 now on the XDA developers forum, but that software is experimental and doesn't include all features that are found in Lollipop. The Z2 and Z3 are not the only existing Sony devices that will be receiving the Android Lollipop update, though. Sony has confirmed that the mobile operating system update will be coming in "early 2015" to the Xperia Z, Xperia ZL, Xperia ZR, Xperia Z1, Xperia Z1S, Xperia Z Ultra, Xperia Z1 Compact, Xperia Z3V, and the Xperia Z3 Compact. It is really just a question of when.

So, why hasn't the Xperia Z4 been announced at Mobile World Congress 2015? It was expected along with the Samsung Galaxy S6 and the HTC One M9, which have already made their appearances. The Verge has also noticed this, and they have commented that "Sony's habit is to release its latest and best in the Spring and not the Summer". It is possible that the Z4 Smartphone could appear in some grand announcement later on, but if that is the case, then it is again just a question of when.

It seems that details about the Z4 change as the probable release date gets closer. According to International Business Times, the Z4 plans to have a screen that is either 5.4 or 5.5 inches. In fact, it might have two types of displays: one with Quad HD and the other with Full HD.

As far as memory is concerned, it should have about 16/32 GB internal memory with 3 GB RAM with a microSD up to 128 GB. The battery for the Z3 is a non-removable Li-Ion 3100 mAh battery, but the Z4 is expected to be at 3420 mAh. As far as the camera is concerned, it should have a 20.7 Megapixel rear camera and 4.8 Megapixel front. Then there are the rumored features of Qi Wireless Charging, IP68 water and dust proof, and LTE Cat 9 connectivity.

Then there is the James Bond connection. It is rumored that there will be some serious product placement of the Sony Xperia Z4 in the next James Bond movie, Spectre. There are even rumors going about saying that James Bond actor Daniel Craig and film director Sam Mendes could have some input in the design of the Xperia Z4.

At this writing, Mobile World Congress is still not over and Sony could pull a surprise at the end and reveal that they are going to announce the Z4 Smartphone after all along with the Z4 tablet. As for the Lollipop update for the Z3, Z2, and the rest of the Xperia series, I would imagine that will be rolling out soon as well.