The Nexus 4 - a phone launched during the end of 2012 is still capable of running Android 6.0 but its low internal storage (the 8GB model) and due to the fact that it has been succeeded by 4 Nexus phones models since its launch ,and so keeping support for this device might be another chore for Google so this model has officially hit its End of life now .
The Nexus 7 2012 - is another device that has ended its update service life and will not get any Marshmallow officially . The Tablet , launched in 2012 was one of the most popular and influential tablet devices to date as it packed a 720p display , a then powerful Tegra 3 - T30L Soc and 1GB of RAM at a pocket friendly $199 . The tablet jump started the small tablet revolution and companies , including Apple launched their own "mini tablets" to address the rising threat (The original iPad mini is now discontinued as well) .The original Nexus 7 has so far come from Android 4.1 and through the years , it flew through many major updates including KitKat and finally Lollipop - The tablet's old hardware ( many OEM's like HTC , LG and Sony dropped support for their Tegra 3 devices early on ,citing lack of proper support from Nvidia) , lack of specs such as a rear camera might have also played a part in getting support dropped , but then again , its high time to upgrade to a new device and if you are on a budget , you can still pick up the Nexus 7 2013 for about $120 and it will get Marshmallow
The Nexus 10 has also lost its ticket to Marshmallow , launched alongside the Nexus 4 , the tablet was one of the first and only devices to feature Samsung's Exynos 5250 Dual Core A15Soc designed on the A15 Eagle platform . The tablet at launched was a thing to look at as its 10" 2K resolution display was a kicker , but as time went on , the dual core Soc showed its weakness and was said to be lagging heavily after KitKat . This tablet however did receive Android 5.1 ,but it will stay there until 3rd party dev support arrives .
Although the three devices are kicked out from cooking their marshmallows , they will get security patches for some time to come .The three devices will however get support from 3rd party developers who are capable of doing some impressive feats and who knows , they might even port it to the legendary HTC HD2 .
Source - ARStechnica