Je viens de voir ça au sujet de la nouvelle màj . A priori il y aurait un genre de coef. qui ferait passer comme par magie une boite de 15 cartes en seulement 8 cartes. Trop bizarre 
Source: General51 from the admin team of Chinese forum.
Before reading the following passage, please keep in mind that once you update to 5.0, your current inventory will be converted to the new inventory so you will find your 4.9 inventory is cleared with nothing left immediately.
If you do not want to pay to win, this game is now "Asphalt 8: TrialBorne" where you try new festival cars about every 2 weeks.
Here I tell you how the 5.0.0 server proceeds your request for opening boxes:
You click on "open" as you are doing now. But the difference is that your unopened boxes will be in "Inbox" section, which means GL renames the current "unopened boxes" after the new "Inbox" with an expire time added.
The system calculates what cards you should get based on the old dropping rate/possibility like the current 4.9 opening boxes.
The system converts the cards obtained in step 2 to new cards at the ratio I have mentioned before: parts*0.5, white tech cards*0.5 while others at the same number. This process is called "update convertion". After this, your new cards will be added to your inventory,
Now some example.
If you open a champion box (30 random cards, one of which should be a V8 engine), and I also assume you are lucky enough to get 1V8 and 29 Avdanced Tech. I have to say you are very very lucky and you will have one blue engine and 29 orange techs added to your new inventory.
If you are not lucky enough that you get 29 other same class B suspension cards, you will only get 1 blue engine and (29*0.5=14.5), 15 blue suspension cards added to your new inventory. (In this case your champion box is like garbage)
If you open a random 5-card-box, and unfortunately you get 5 D-class suspension cards, only 5*0.5=2.5, so 3 new grey suspension cards are added, which means you should get 5 cards but in fact you only get 3.
If you open the same random box, but you get 5 different cards, congratulations to you that you are lucky enough to still make it a 5-card box.
Other update info:
I don't know whether you can exchange cards for fusion coins after 5.0, but I'm very sure fusion coins are required to pro any vehicles then.
Gift hunt is cancelled in 5.0, but still unconformed.
Pro is not available for motorbikes.
Festival cards will still be festival cards just with different card IDs. All pro-only cars will require specific cards to pro. So all Mclaren F1 racing cars and atom V8 will "become festival like cars" in the new version.
Since there are still Batista and TD ATS unlaunched, GL has another 4 weeks to adjust any settings on 5.0. Before 5.0 update is pushed to us, we may have a 4.9.1 update where we have FE events but prokits is not changed.