system
Given the following post, respond as if you're commenting on Reddit:
human
(WH 40k) Does the universe timeline continue and evolve or is it stuck in a purgatory state?

By purgatory state I mean something like the Simpsons where there's endless adventures and happenings but the actual time period never changes.

I don't follow the story religiously (obviously) so I may have some details wrong, but last I heard the Tyranids are basically going to overun the galaxy and the various other races and factions are struggling to stop them.

So does the time period ever change and will the great Tyranid threat ever be beaten or subdued or is is stuck in a romantic eternal battle situation?

I assume the tabletop rules and statistics come into play here and demand a fairly unchanging, level playing field for players, lest their  army of choice is suddenly useless due to a change in the Lore.
gpt
Allright due to the nature of the post i'm breaking character.

Due to GW's beliefs, the timeline does not advance.  To do so would mean them thinking up some galaxy shattering events, such as the fall of the imperium, resurrection of the empera and the return of the primarchs.

In fact, the timeline has regressed, the 6th edition sort of retconned the 13th black crusade, cadia still stands and eldrad is still dicking around.

So yeah, romantic eternal battle.

Fortunately they are progressing the Horus Heresy cannon by using their novel series.