It's really hard for me to predict what could come in on the car front, we never got much in the realm hints before Kaz made the silhouette posts on Twitter. Given what's in the game now I could see the Ford Mk. IV come in to complete the '67 Le Mans trilogy, but beyond that I really don't know what specifically to expect. The only cars we definitely know to be getting scanned are those drift cars "leaked" on Instagram, and a few SEMA award winners (I don't recall hearing anything about any of the Pebble Beach winners, but those could also be underway). Given the Chris Holstrom Nova I think we could see the SEMA cars at any point, but the drift cars I feel would come in their own update/DLC pack. We've consistently getting some classic '80s & '90s Japanese sports cars, so I wouldn't be surprised by an old school NSX, R33, Lancer, WRX, and/or maybe an older Nissan Z model? There was also that interesting bit of Lamborghini licensing in the credits, so maybe more Lambos (any of Miura, Gallardo, Murcielago, Aventador) could come?
On the track front we've got a few leads. We've known about Deep Forest being under development for a couple months now, and we don't know when that project started. And then the game launched with Scapes locations at LeMans, meaning a team had to have been sent down there after Scapes technology had been fairly developed. Especially now given that Gr. 1 has started making it's rounds in Sport Mode, I think LeMans is the biggest contender (honestly I was expecting it last update, Monza caught me completely off guard), but Deep Forest is still on the table.
As far as new layouts go, Blue Moon has some visible (but under-developed) infield routes, we know of a Northern Isle infield/Gymkhana course (it's in the opening sequence), there's that hidden Kyoto area, and Dragontrail and Tokyo are named in such a way to have additional layouts available (so are Fisherman's Ranch and Colorado, but I don't see a big push for extra rally content right now). I personally lean more towards the Blue Moon prediction, but the Kyoto and Lake Maggiore layouts sorta came out of nowhere, so I wouldn't necessarily discredit Tokyo or Dragontrail too quickly. We also know that PD has scanned/gotten license for Pikes Peak and Isle of Man, but those don't really fit anywhere that's been given focus yet. There was also the announcement of an event at Barcelona later in the year, but if that's even a thing I feel like it's a bit far off still for that to be coming soon.
It's hard to say what I actually specifically want to see, cuz there's so much good stuff out there. I don't have a huge preference on specific tracks, I just want more ribbons to drive on (though preferably more that are suitable for Gr. 1 & 3, cuz it feels a bit thin there). That said I do really hope Le Mans comes in the next update. I'd also love to see Seattle make a return, primarily due to the fact that it's my home town, and I'd be intrigued to see how PD lays out the route with the modern configuration.
There's so many cars it's hard to lay down any specific must-haves, though I will say I'm surprised the game launched without any sort of road-going Audi R8, V12 Lamborghnini (Aventador), Ferrari 488, or Nissan Z, these all seemed like key modern cars in their respective brands that would also fill out the various N classes rather nicely. I'm also surprised there wasn't at least one other member of the "holy trinity" to help out with the N1000 class, especially with the Porsche license released from EA. Of just those I listed I think I'd be most keen to see the Aventador and the 918. I also hope that some of the Gr. X cars start getting regrouped into new classes, it'd be fun to have a sanctioned truck (and maybe with it an additional grouping for rally) class and a hybrid/EV class, I wouldn't mind the Raptor or the i3 getting getting a few new friends. But above all else I hope to see classic/historicv/vintage/retro eras get separated into their own classes as the car list balloons, it'd be absolutely wild if we get the Mk. IV Ford to complete the GT5 '67 Le Mans trilogy, and then another similar-era racer (maybe Porsche or Alpine) to fill out a new classic racing class.