Friend and I had a conversation regarding the cars used on screen, thats when I asked myself if anybody has ever attempted to locate where they are today. I know several are in private collections as they were sold at auction. But I would love to compile a list. I'm also specifically wondering about the DOTM wreckers.
Any info will help! Ill update the post as info comes in.

 

I'm curious as to where both the actual filming props are located, and the status of each car model / maker used in the movies.

You're definitely right that the Barricade Saleen Mustang was sold at auction, I just don't remember where. At least one Arcee bike was sold as well, I think Chromia.

As for the car models, I know the following (if the car name is still used but gets a new iteration each year, I counted that as still existing) :
Bumblebee - Camaro - still being sold / getting new models to this day! (although rumor has it it's on the out)
Ironhide - GMC Topkick - car was discontinued around 2009-2010
Ratchet - Hummer H2 - Hummer brand was discontinued around 2010 (although the Ratchet Hummer was pretty custom)
Jazz - Pontiac Solstice - Pontiac brand was discontinued
Sideswipe - Chevrolet Corvette Stingray Concept - never made it to market
Skids - Chevrolet Beat Concept - revised into the Chevy Spark, which is still sold today
Mudflap - Chevrolet Trax Concept - never made it to market as it existed (although the Trax name lives on)
Jolt - Chevrolet Volt Concept - still sold to this day
Dino - Ferrari 458 Italia - succeeded by more recent Ferrari models
Que - Mercedes Benz E550 - no longer made, and I believe it was extremely hard to come by especially in the US
Wreckers - Chevrolet Impala - obviously heavily custom, but the Impala line still lives to this day
Crosshairs - Chevrolet Corvette - still sold to this day
AOE Drift - Bugatti Veyron - discontinued in 2015, but still a very popular high-end / collector car
TLK Drift - Mercedes Benz GT-R - still sold to this day
Hot Rod - Lamborghini Centenario - only 40 were ever made!

Barricade - Saleen Mustang - Saleen Mustangs are still sold to this day
Sideways - Audi R8 - Still sold to this day and still always locked at auto shows  
Soundwave - Mercedes SLS AMG - phased out in 2015 and succeeded by the AMG GT, which was not a gull wing car
Lockdown - Lamborghini Aventador - newer versions still sold to this day
Stinger - Pagani Huayra - only 100 were ever made and sold out in 2015
TLK Barricade - Ford Mustang - still sold to this day

 

So many expensive cars...sometimes I wonder where did all the budget go for these movies..

 

You'd be surprised how little went to cars considering the car companies considered Transformers a commercial for their products; oftentimes they paid Paramount to feature their cars and not the other way around.

Plus, Bay signing a deal with GM for the first movie famously helped bring things within budget.

EDIT: I should also add that part of the car manufacturer deals was in exchange for featuring certain cars, the automakers provided all of the junker cars for Bay to blow up real good. So that was further savings for the production.

 

They're bringing the Hummer back as an EV!

 

Audi was pretty mad over what happened in ROTF.

 

Why you want to ask them for their auto-graphs?

 

- Several Camaro Bumblebees, one Optimus Prime from movies 1-3, and the only Roadbuster & Topspin (Volleybot) vehicles are in a private collection

- Both versions of Barricade, three Camaro Bumblebees, Age of Extinction Rusty Optimus Prime are in another private collection

- Michael Bay owns the other The Last Knight Barricade Mustang and one of The Last Knight Bumblebee Camaro and he sold the mint condition Dark of the Moon Camaro where it is most likely in private hands

- Paramount displays movie 1-3 Optimus Prime at their studio tour

- One of the 2007 movie Saleen Barricade is on display at the Celebrity Car Museum in Branson, MO

- Galvatron and the Western Star Optimus Prime trucks are with Daimler/Western Star in the states

- Mercedes Hound is with Mercedes in Germany and Mercedes Drift is also in Germany but unsure if one is privately owned or both cars are with Mercedes Daimler

- Ice Cream Twins truck was previously on display at the Petersen Automotive Museum, but not currently

- Jazz Pontiac Solstice was sold a decade or so ago at Barrett-Jackson and is in private hands.

- GM still has many copies of the vehicles and Paramount has some.

 

The Impala was actually discontinued last year. The last Impala was completed on Feb 27, 2020. And then the main plant that built them was shut down.