I can remember only a few years ago where the vast majority said 3D printing will never really impact on our hobby.
Laughable now.

I'm VERY tempted to get on the bandwagon and buy a printer for my large scratch-build cars.

I have to wonder though - WHICH major model kit company will be the first to offer 3D print files of some of their plastic kits?

Yes, some will scoff - but it WILL happen as more and more people get 3D printers and stop buying plastic kits.
It's the FUTURE and there will be a BIG market for such files if Airfix, Revell, even Tamiya get on board.

Kodak laughed at digital camera's and thought they were safe carrying on just making roll film.

How long I wonder - and I bet it won't be donkeys years away...

There are already a lot of people offering files for models to print. I have copied some parts from plastic kits that I have broken to print instead of ask for a replacement part. The issues currently are resolution and expense of the printers. You can buy fdm printer like the creality series for a couple of hundred bucks, but you will need to do a lot of filling and sanding to get rid of the print lines from these printers.The other option is a resin printer.These are more expensive than the FDM printers and generally have a much smaller print volume and the resin is much more expensive than the plastic filament for the FDM printers.The resin printers are very high resolution and can produce parts that are highly detailed and dont need any sanding after printing.

The other problem with 3d printing is they printers are quite slow. I am making some parts for my phone home one spaceship.One of the which is about 10 inches in diameter and 3 inches high will take 129 hours to print.the resin pritners are really slow too.

The cost of the models available for download is very variable.There are tons of free models and some that are just a couple of bucks, but for the bigger models like studio scale Star Wars kits the models cost a few hundred dollars.

I think some of the plastic kit manufacturers may be a bit worried about the rise of 3d printing and I think in the next 10 years they technology will be pretty close to be able to produce parts of a similar quality to some molded parts.