Stellaris is also far younger than EU4 or CK2. If we take CK2 and EU4 as our baseline, we can expect Stellaris to see regular updates and concomitant DLC for at least half a decade. That may be good or bad depending on if you like the new features, given that the Stellaris team seems to be much more willing to play fast and loose with core gameplay compared to the other Paradox dev teams. Stellaris v2.0 seems to be a much more extensive overhaul than most of the other games have received judging by what we know, and discussion there has been a bit heated at times.
I think I'm generally in accord with Reelya here, though it should be noted for the sake of bias that I do have a bit of an emotional attachment to a company whose work I've followed since...oh, heavens, Europa Universalis 1 back in 2001-2002. The old model was in fact very similar to that which was outlined with a minor caveat. To wit, the older model for game development Paradox followed was slightly more generous than the "EA Sports" model of a new version like clockwork; rather, they released new expansion packs that completely superseded older versions. Subsequent patches were released primarily and eventually solely for these new expansion packs, leaving those players who did not purchase the expansion packs entirely out of luck. The official reasons for the new DLC policy were to avoid this and increase version intercompatibility; a player who does not own a DLC can still play with players who do own the DLC, as well as still enjoying the latest bug fixes and free features. The unofficial reason was probably money, to be cynical; DLC may be individually less expensive and more optional, but in aggregate it does cost a fair bit more. I at least take advantage of cherrypicking and sales where and when I can to deal with that issue.
By the bye, I fully expect the DLC policy to bite them on the posterior for the precise reason it has EA/Maxis and The Sims. At some point, they won't be able to keep strapping new features onto the old core game without the entire mess collapsing. At some point, in other words, they'll need to create Crusader Kings 3 or Europa Universalis 5. At that time, they won't have the luxury of years of continuous development solely on the new game, so the new base game will almost certainly be released lacking features from the previous version that at least some players will value highly. This happened with EU4: on release, many people immediately compared it to EU3 plus expansions and found it wanting, even considering that the fanbase does tend to be a bit ornery at times.