Well, let me give the clue hunting a shot.
Let's start by the most obvious: the birthday cake. It's the game's 1st Anniversary update.
On the top-left corner of the board, we have a slot-machine drawing, with two cars pointing towards a bag of credits. This suggests that this update will introduce the ability to trade a duplicate wheelspin car for an equivalent credit reward.
Below that we have the numbers '11/250', and below the '250' we have '2750'. As it stands right now, you can earn a total of 2500 gamerscore from Horizon 4. But, if they introduced 11 new achievements, for a total of 250 more gamerscore, the total you could earn from the game would be 2750.
Then, there's the truck, with pipes. Note how they crossed out the front of the truck. Trucks are composed of two major parts: the cab and the
trailer. Without the cab we are left with a trailer carrying a bunch of tubes on top. On the internet, video streaming sites are referred to as 'tubes'. Combine the two and you have a trailer that will be shared across their media, for this update.
As for the fish with the incredibly long tail, you would guess the Mclaren Speedtail. But that fish is fairly regular, nothing particularly fast about it. The term 'LongTail' is associated with at least two highly requested Mclaren models: the 600LT and the 675LT. I find those more likely.
As for the the spider dropping down, with the number 19 next to it, it's a car with either 'Spider' or 'Spyder' in its name, from 2019. The Porsche 718 Boxter Spyder comes to mind, especially considering the 718 Cayman arrived recently.
The spider could be an allusion to 1919 car, that is a barnfind... covered in spiders.
As for Sonic the Hedhehog, I'd say the 'Gotta Go Fast!' phrase is just there because it's Sonic's catchphrase. The actual car being teased is, as said already by another member, likely the 1953 Fiat 8V Supersonic. It's been in Horizon 3, FM7, but still isn't in Horizon 4.
Finally, last month we had toy Porsches on the desk, this time we have tissue paper. Which suggests this update will make fans cry, presumably of joy, hence the need to have tissues in hand.
The rest, I seriously have no idea.