The danger of sticking with a working title for so long is that you run the risk of effectively undoing months or even years of marketing the moment you slap that new moniker on—after all, names tend to stick, no matter what they are. On the other hand, Next Car Game isn't much of a name, so say hello to Bugbear's Wreckfest. Hello, Wreckfest! I can't promise I'll remember your new name, but I'm glad to see you've introduced "true" internet multiplayer in your latest early access build.
18-player multiplayer is the Big Thing of Wreckfest's Build #6, and you'll be able to utilise this in the game's Racing, Demolition Derby, and new Deathmatch and Team Deathmatch modes. In the last two you're allowed to respawn upon destruction and get right back into the race. Which is nice.
24-player multiplayer is on the cards eventually, but "optimizing the network code" will take the team a bit longer, so you might have to wait a while for that, as noted in the Bugbear blog. Or the Bugblog, as it should probably be called.
The Steam Early Access update page has a full list of all the changes made in Nex...Wreckfest's latest update, including "Improved skid marks", and other things that didn't make me giggle like a ten-year-old.