To add to this:
The only thing you're getting by pre-ordering is a car. If you're paying the game normally, you'll end up with a plethora of cars and bikes already, so you're not really missing out on anything special. (which, tbh, is decent on CDPR for not banking on huge FOMO)
You can always wait for the release and look up reviews and (more importantly) first hand player experiences on here/reddit/youtube/wherever you consume gaming media, to avoid spending money on a potentially subpar product.
Just a disclaimer: I'm also very much hyped for the DLC, and plan on getting it day one (if all goes well), but I'll wait for reviews and impressions first. :)