Not everyone is going to buy Lord of Hatred on day one, and that is totally fine. The 3.0.0 patch that comes with it is huge, and a big part of it is free for everyone, expansion or not.

So if you are wondering whether Diablo 4's next expansion is worth it for you right now, here is what you get with the expansion vs what is going to be available for everyone.

Free for All Players (Patch 3.0.0)

Skill tree rework for every class, with over 40 reworked choices and 80 new options (some old aspect powers are now skill variants)
Level cap increased to 70
Torment difficulties expanded from 4 to 12 (check out Mekuna's Guide to T12)
The Loot Filter (you can finally hide, recolor, and sort gear drops)
Map Overlay and Pathfinding system (which lets you follow a path without staring at the minimap)
Itemization overhaul (damage multiplier rework, Unique tempering, Legendary Aspect updates)
Pit overhaul
Inventory stacking up to 1,000
2 out of 3 Bonus Skill Variants per skill (the third requires the expansion)

Requires Lord of Hatred

Lord of Hatred campaign and the new Skovos region
Warlock class
Paladin class
Horadric Cube crafting system
Talisman (Seals and Charms with set bonuses)
War Plans endgame system
Echoing Hatred challenge/survival mode
Fishing (nothing special, but a fun little side activity. No big rewards attached to it)
Additional stash tab and character slots

What About Season 13?

The Season of Reckoning is also accessible to everyone. You can progress through Season Rank, earn rewards, and play the Tower and Leaderboards Beta (once those go live on April 30) without the expansion. However, around 25% of the Season Rank objectives are linked to Lord of Hatred content.