I can see why you chose Skyrim for comparison because of the open world aspect, but I believe that Diablo IV is much different, like others before me in this thread.
Now, to your original post: Let me kindly try and explain how I think it is going to work 
At the release of the game, before season
We get to level 50 and start grinding paragon levels (up to 50, max) for a total of 100 levels. That is the main goal, along with finding epic gear and try to achieve our dream build, whatever that may be. To be real, only a few of us will actually have the time to invest that many hours in the game before launch of season.
Now comes season
Just a few weeks after release, I think Joe Shely, Game Director, promised
… And this is what I expect to reset, based only on how resetting worked for Diablo III (keep in mind, none of us actually knows)
You will keep all your unlockables (horse and cosmetics) along with ‘global’ ressources like herbs and everything else, but these items will only be available to your non-season characters.
For seasonal characters you start with a clean slate.
Words are often just opinions, including mine
Now, others in this thread mentioned that the story does not reset a long with quests, I do not know what new things the beta will offer, or if the map will reset (which I assume it will) and someone also mentions that you will keep the bonusses from your statues of Lilith - again that seems weird to me, how would that be fair to players who only start at the beginning of season?
That said, until I see official sources, I will simply interpret that as speculation.
Again, none of us regular players actually knows what Diablo IV seasons will be like. What I do know is that the devs will talk more about season before it launches, so you will have ample time to decide if seasons - or the entire game are/is for you 
Personally I like seasons for the new content. I do not like the idea that content might be exclusive to seasonal players, as it splits the community in seasonal players and non seasonal, but like Diablo III, I can learn to adapt to it.
I hope seasons for Diablo IV is a masterpiece in its design, but until I read/hear official word from the Diablo IV development team about how the season is designed, I will not worry too much about it 
After all, levelling in Diablo IV so far has been a breeze, compared to Diablo II and Diablo III.
Edit: Corrected Diablo IV to Diablo III in the final sentence, and improved grammar.