Greetings fellow Nephalem! Let me start by saying that I am absolutely loving the game. Blizzard, to my surprise, nailed the story, tone, class design, and overall feel of the game. I love the damage systems and find myself diving into how I can min/max mechanics and builds! My ONLY issue, is where all this goes… The idea of a fresh start on seasonal content is great, and I’ve heard devs talk about how seasonal mechanics will allow you to power creep your past toons on the Eternal Realm, which is really cool. My only worry, is that if all the “must do” content is on seasonal realms, what will drive us to come back to the Eternal Realm? What “big baddie” will we feel compelled to slay, rather than continue our push with the new season? When you think about a new players experience, seasonal stuff is cool, but I doubt they’d want to continue playing through the story if it doesn’t feel like a continuation from their initial journey on their first Eternal toon. It just feels disjointed. I have a few solutions that I’d love feedback on, as I think their are ways to solve this issue, and I wonder if the devs already have some of these things in store for us.
Firstly and most importantly, I think any sort of continuation of the story in future DLC has to be on the Eternal Realm. This would help formulate the game progression in a way that allows for interesting expansion of the game through seasonal content, while players will still feel a connection to their main on the Eternal Realm, that which they experience the RPG aspects of the game on, rather than just feeling like their toons are just “stat sticks” derived from your desire to min/max. The story was fantastic! And it built upon the fantasy of my toon so beautifully! Bring me back to that! It would be so cool to gear up with new aspects in seasonal content, knowing that their are HUGE story bosses on the Eternal Realm that I’ll want higher tier gear to complete. There are definitely a few ways they could do this, but hearing from D3 players, it seems the Eternal Realm got shelved with a small minority of players ever engaging in it, which subverts the purpose of it existing at all. The seasonal “fresh start” model is awesome, but it pulls me out of the role-playing dynamics that the story chapters worked so hard to develop, which is easily remedied in the case that we return to these characters, or at least have the option to, whenever we get story continuation like with Mephisto.
Second, expand the PvP on the Eternal Realm. If we can agree that it’s valid for players to want reasons to play the Eternal Realm… PvP is an easy win. Since seasonal content is geared towards PvE and new mechanic progression, add some fun PvP stuff for our long-term toons. Just like the last point, this would add a lot of value to players getting new gear on their seasonal excursions, knowing that they’ll have new toys to use on their past toons. I think this could align with the devs intention on adding a dungeon queue system when you walk up to a dungeon door. Simply have PvP portals that queue you for basic 4v4 brawls. This could even take inspiration from Destiny’s Gambit PvP mode, wherein these brawls could have PvE enemies to defeat for buffs or some advantage (I’m a league player so you can assume the way in which I see this functioning 
).
Third, I think they should add some additional world events that aren’t just slaying a few bosses. They are cool, but my mind goes to the old Halo Firefight mode. Again, maybe using a portal system, take us to some demonic area with MASSIVE waves of enemies that allows players to split up and take on different bosses, that leads into one big fight. This would really just be an more expanded version of what already exists, but walking up to a Legion Event that gets swept by a bunch of lvl 80’s isn’t compelling, which I why I point out that the area should be big enough for us to split up, with multiple sub-bosses leading into a big fight.
Lastly, RAIDS RAIDS RAIDS! This is an idea of talked about with my buddy I play with, and it feels right. With Nightmare Dungeons and most general content being wiped so fast due to how intensive the damage scaling is in the game, we need to have areas and boss encounters that truly strike fear into us… like the first time you encounter The Butcher. Some sort of raid zone, or instanced raid area, would let the devs really flex their muscles with high-level mechanics and devastating enemy encounters. Something like this, could lend itself to having more support driven aspects, and maybe even a support/utility class at some point.
I know a lot of this might seem like I’m reaching, but the point of this really is to explain what would keep ME coming back season after season. Obviously any of these suggestions crystalizing in reality would be FAR down the road, even if they already have some of these things in the works, but I’d be very curious what the community thinks of this outline, and if the devs have had any of these conversations.