I'm sorry, but all I have to say is that there are a few AAA video game development companies starting to support their video games for more than one year now, even two years.
Techland CEO just said last week? That they will be supporting Dying Light in all of 2016 and possibly for a few months in 2017.
CD Projekt RED even though they are going to release the last expansion pack for The Witcher 3: Wild Hunt Blood and Wine for sale sometime before 2016 ends they plan on supporting with at least patches for years to come. Even though they are working somewhat right now on developing Cyberpuk 2077.
VALVe's Source Engine is still being updated by VALVe like two weeks ago Half-Life 2 and the Source Development Kit (SDK) got some texture updates for the 2013 Source Development Kit (SDK).
Tripewire Interactive supported Killing Floor for six years I guess.
SONY Computer Entertainment and Evolution Studios released DRIVECLUB for sale in 2014 and are still updating it with DLC's and patches. October 7th, 2016 will be two years since DRIVECLUB released for sale and is still getting DLC's released for sale and patch. I think 2016 is the last year of support DRIVECLUB gets.
Bethesda Game Studios can do it it's not impossible.
Bethesda Game Studios is working on developing somewhat The Elder Scrolls VI right now anyways. Once they want to fully go into developing The Elder Scrolls VI they can have a skeleton crew of employees working to develop more DLC's and expansion packs for Fallout 4.
Or maybe that is what Bethesda Game Studios Montreal opened up for.