I love this idea to be honest with a passion.
One of the most frustrating aspects of the lore to me has always been the effect of the name of the game. Back when it first started Rick Priestly wanted to call it Rogue Trader, problem was they had been working on a lot of 2000AD IP games at the time and had released the game Rogue Trooper which they were concerned that people might get confused so someone suggested well it's Warhammer...and it's 40,000 years into the future...so...
For the earlier editions it wasn't a problem because there was no hard timeline, there were mention of events but no hard chronological order. Once the focus shifted to recording the dates and orders of events the game lore started to become a hindrance in my opinion because we were starting to lose some level of freedom if we were lore nuts. It became the accepted norm that there simply was nothing beyond the 41st millennium and the reason was it was all about the name Warhammer 40,000 .
I remember discussions and it was always a case of being told it's Warhammer 40,000 not Warhammer 41,000. For a lore junkie wanting to play in the current meta it was just down right frustrating, it started to lose importance to me because no matter what you did time was running out and as more stuff got added to satisfy the needs of people that loved the timeline it slowly began to creep to 999.M41 and we were running out of room to play around with things.
If you take into consideration (without going into too much hard science because that's a bit mad for a fantasy sci fi setting) things like regular time distortion involved at it's most base level in 40k, the base measuring stick being warp travel, you could effectively play a game set in gathering storm take a warp jump and effectively write yourself out of the lore because the ships may not emerge for another three years. This was something I was always very vocal about with the whole two minutes to midnight thing in the past, not because it was humanity making a last stand but because of the crushing claustrophobia of trying to justify events knowing it'll never move on past 999.M41. It was less about the stories of heroism and desperation and to me felt like being stuck in a perpetual loop where you have over slept and are rushing out of the house, toast in one hand, trying to do up your belt with the other and desperately trying to get to the station to catch the train.
I think the timeline fell prey to the dark shadow of officialdom and to be honest now there is so much more freedom with such a simple concept as we just don't know what date it is. This is actually a really good move, the events of the timeline still happened in the same chronological order, A still leads to B which leads to C, but there is now doubt over the exact moments these events took place. It's still about ten thousand years or so since the Heresy but the exact dates of things between now and then are kinda grey and hard to pin down.
This also plays nicely into the mess that is the Administratum with the horrendous book keeping, telepathic dial up email system and billions of employees religiously devoted to their given tasks being blind to the greater events of the galaxy. It rebuilds the dystopian setting of the game that I feel had been slipping of late in favour of 'bolter roaring lets destroy this well established thing we set up years ago' and hopefully we will maybe see more of the setting in a new light which will let the history take it's time to spread out and grow and not feel like we are being painted into a corner.
So yeah I like it a lot.