So, that's what the new update is for...

Pretty sure the 4.0 update is a massive free rework in itself already

How many DLCs does Stellaris already have; 20, 25?

I track it as 28 expansions, though that includes 2 free ones, 2 "season" bundles, and an upgrade pack that mostly consists of goodies (plus a single bit of content) - so 'only' 23 "pure" DLCs. Indeed. I don't think they've posted the final release notes yet, but the highlights of the preliminary release notes sounds pretty big. I'll give it a release or two to shake out before I'll try for myself.

They posted the release notes a couple hours ago: [Dev Team] BioGenesis + 4.0 'Phoenix' released (checksum 1ae3)

--- 9 full expansions
1 mechanical expansion
1 narrative expansion
6 story packs
6 species packs
cf. Downloadable content - Stellaris Wiki

Thanks for the answer. 23 DLCs for at least 9.99€ without discount is a lot of money. I think I will not even try to get them all...

So I'm happy about the new DLC, as long as the game is stable and there are meaningful ideas, you are welcome to continue. I've played this game for more than 800 hours and haven't been bored for a second.

giving a look at the stellaris discussion board on the steam website, it looks like this recent 4.0 update was released before being ready, with reports of performance being much worse (the slow "turns" start to happen much earlier) and the AI can't seem to follow the new / changed rules correctly and regularly break itself.

Looks like there's a good 4/5 months of dev work required before i'll update from the current Stellaris i use, good i always keep the gog "working" offline installers in case new versions go wrong (Dragon Age Origins, looking at you)

So how stable is the game now? I remember back in the day when you reached later stages of the game it lagged. Did they fix that?

unfortunately for now, the new update seems to make it much worse :

https://old.reddit.com/r/Stellaris/comments/1kfeyuc/stellaris_401_first_performance_test_result/
https://steamcommunity.com/app/281990/discussions/0/596274028959803329/

Hopefully things will get better in future patches of that Stellaris 4.x.x line, but it's hard to be optimistic after reading those

Stellaris expansions are regularly on sale for -40/-50% one year or two after their initial release.
So right now we have the last one at full price, the 3 previous ones at -20%, and all previous ones at -40/-50%.

I would advise everyone but the most hardcore Stellaris fans to wait until at least a 40% discount before buying an expansion. Actually, I think even the hardcore fans should do that, especially if they would rather wait for the expansions quirks to be all fixed and balanced.

Some reviews say that the DLC made it worse, I would wait a while before purchasing this

Even at a 50% discount it's still a lot of money for just one game. If I had known that a few years ago I would have waited with my buy of Stellaris.

The game itself is available for 10€ right now.

The expansions are extra content that is not required in any way to enjoy the game. Nobody is expected to buy everything at once, or even to buy anything at all.