I'm sure others with better knowledge will be more specific but:
In short:
What would be the last decade in the US that wide release movies would be shot, edited and released on film?
1990s.
A modern movie, shot on film today (or last 5 years for example: Wonder Woman, La La Land, etc for example) would still get the digital treatment, once the film is in the can, through post production (scanned and edited) and into distribution and presentation (digital presentation at your local movie theatre).
In 2002, the Digital Cinema Initiatives (made up of MGM, Paramount Pictures, Sony Pictures Entertainment, 20th Century Fox, Universal Studios, Walt Disney Company and Warner Bros) was formed to create standards for digital cinema. According to its first release in 2005, films must have at least 2k resolution, the film must be transferred on a DCP or a Digital Cinema Package, and the film must have stringent encryption measures.
Part of the complication in an answer like this is the Cutting Room - the cutting process used in the linear editing of the negative - a hugely laborious process in terms of people and time - and expensive process that had been the norm in post production for decades. i think there was a huge push to get past this as it slowed the process of editing considerably (Unless you were Stanley Kubrick, he loved the editing process far more than the process of capturing it). I recall seeing paperwork for cutting room process and procedures in the 80s but this was gone by the 90s.
The desktop revolution and the introduction of computers enabling non-linear editing was a huge and swift revolution - the first digital non-linear editors arrived in the 80s, computer power dominated in the 90s and the desktop power took over over by the end of that decade - across the board in both long form and short form.
Regarding the establishing of the DCI DCP's, the first mainstream Hollywood movie to distribute both on a hard drive and on 35mm reels was 2005s Inside Man. Note, although shot on film - and developed and processed (bleach bypass etc) - the post production process was all digital once the resulting analogue process had been scanned (digital intermediate).
In the early 1990s, digital studios like Cinesite were created to take advantage of what digital intermediate offered long form (digital was already standard for short by then), using tools such as Flame and Inferno. 1993 Super Mario Brothers would one of the first to go through this process. By the time I was looking at those tools it was mid-90s and those tools were standard by then. That same decade was the last time I used a Steenbeck (16mm, KEM for 35mm). Those same digital tools lasted maybe less than five-ten years before being upstaged by desktop tools that could run on laptops.
The Phantom Menace had a limited digital projector release in 1999.
One of the first Hollywood films to be an entirely digital post process was 2000s O Brother, Where Art Thou?
Digital intermediates accounted for more than half of Hollywoods production by early-mid 2000s.
So, without delving too far, 1990s would see a combination of the photochemical process being replaced by the digital process, post production - including editing - becoming almost an entirely digital process by the end of the 1990s; and digital distribution in theatres taking over traditional reel by mid 2000s.
In hindsight it looked like a pretty swift takeover from late 1980s to mid 2000s - but the 1990s was the big rollover.
The industry press was almost entirely digital in its coverage by the 1990s.
The last time you could conceivably get to see a reel, theatrically, in the US, that had been analogue from capture, process, edit, post, and distribution was probably very early 2000s, and already in dwindling availability by then; that said, the movie in question is far more likely to be an art house movie than a Hollywood blockbuster - for the latter you are probably looking at the 1990s.
Tarantino's Hateful Eight in 2015 had a largely analogue process, from capture to finish, timing, apparently avoiding the digital intermediate process (for 70mm), to distribution, and was the widest release in 70mm film since 1992's Far and Away. It required a large number of theatres to be retrofitted with projectors to screen the movie.
The year before, 2014, saw 'Anchorman 2' announced as Paramount’s final release on 35mm film, and that Wolf of Wall Street was the first major motion picture to be distributed entirely digitally.
https://arstechnica.com/gadgets/2012/06/the-silver-screen-no-more-distribution-of-film-to-cease-by-2013-in-the-us/
Celluloid no more: distribution of film to cease by 2013 in the US
Recommend a viewing of Side by Side (2012)
