Ubisoft have announced the post launch content for AC Odyssey which includes 6 mini episodes split into two parts, one about the origins of the hidden blade and the other about the mystery of atlantis. They also announced that the AC Odyssey season pass will included Assassin's Creed 3 and Liberation Remasters which can also be purchased as stand alone, similar to AC Freedom Cry. And yes, the remasteres will be on PC :)

Source: https://news.ubisoft.com/article/Assassins-Creed-Odyssey-Post-Launch-Details-Revealed

So, as you've seen in AC Origins, it had an online store with outfits and certain cosmetics you can purchase with real money, not Drachmas, but in AC Odyssey, the store has a few new features.
If you've looked carefully in AC Odyssey's store page, you could see that the Deluxe edition gives you an XP boost, and that reminds me of other XP boosts in last year's games. where it increases your XP gain for a limited amount of time. AC Odyssey's XP boosts seems by far not different at all.

Thanks for reading,
The Assassin's Creed Lovers group.

I am guessing you've heard about AC Odyssey letting you choose between a male or female protagonist, well, if you get a hard copy of AC Odyssey, there is a minor detail you might notice.
AC Odyssey's box art will have Alexios (the male) on one side of the cover and Kassandra (the female) on the other, so you can switch to the one you like.

Thank you all for reading,
The Assassin's Creed Lovers group.

Hey guys and girls!

Although this group has almost 300 members, the discussions are pretty quiet at the moment. I would just like to ask you, if you don't mind, could you please go into the group discussions thread and click the grey box that says "Subscribe to Forum" if you would like to stay notified about whats going on in the AC world. We would love more active users in their and I feel like alot of people just forget that the discussions exist so it remains pretty empty.

Thanks and have a great evening :)

So the creative director of AC Odyssey did a reddit AMA, and when asked by a fan about there being a canon ending, he said that there will be a book released later which will tell the story of kassandra and tell the canon events of the game. The events that take place in the game are up to the player and will not effect any part of the AC universe out side of the game.

https://www.youtube.com/watch?v=40p33q2u8AU