For starters, the printing process is extremely expensive so that's a huge deterrent for lots of companies and the reason why so many have perished.
I work for a relatively new Magazine company that exists solely online because quotes came in between 25-100k to print the magazine with a minimum of XXXX orders.
If you have a decreasing readership, you cannot afford to raise your price but you also can't afford to lower it so it puts a lot of companies between a rock and a hard place.
As a result many are now gone.
However I don't think they'll ever die completely.
I heard this quote somewhere, can't remember the specifics but you get the gist of it:
anon said:
You can see boobs on the internet so does that mean you no longer need them in real life? No of course not because sometimes you just want to touch them and feel them; there will always be a sense of touch involved which is why print media will never die
Sure you have all these companies that offer services where you can pay a subscription to get access to a bunch of mags but ultimately people are still going to want a hard copy. Perhaps not in the same demand as they once were but it will always be there.
I guess you could say the same thing for books really.
However the argument here isn't about books, especially considering magazines are 90% photos.
Which is another problem because every other Joe Blow thinks he's a pro photographer because he spent $1000 on a DSLR.
Anyways what I'm getting at is that I don't think they'll completely disappear.
People are going to always want a hard copy (tactile feel, easier on eyes, some people collect...etc)
However, I do think that the magazine content will drastically change to a more scholarly, scientific approach.
As stated above many of those mags were just pictures of really cool cars, a basic DIY, perhaps an informative tuning article, a hot girl and lots of ads and you can easily eliminate 90% of that stuff thanks to the internet and every wannabe facebook page.
The scholarly articles, tuning articles, reviews...etc are still things people want.
Sure people have video reviews of cars and ELI5 articles regarding tuning over the internet but a well written, thought out piece of text is better than 90% of the videos/brief info there is out there on the internet.
Most of these things aim to entertain not inform, sort of like how TG is ragged for not being informative.
People still get entertained with well thought out reviews that incorporate scientific information, credible sources and lively language.
So it may be a struggle for the remaining companies but those that make it will most likely shift to this sort of attitude.
tl;dr: they won't completely die out but those that do stay around will transition into a different form of magazine.