If you already own the ‘Blood for the Blood God’ DLC for Total War: Warhammer, it will automatically apply to the upcoming sequel. That bit of news comes from Creative Assembly, who confirm that the one purchase will cover both games.
It will work both ways too; so if you own Total War: Warhammer 2 and purchase the Blood DLC, then buy the first game, it’ll retroactively apply. That aspect is also confirmed, on the Total War Facebook page.
Having to buy an additional piece of DLC to unlock ‘Blood and Gore’ has been a staple of recent Total War games. The standard explanation from Creative Assembly is that it can’t be included in the base game without affecting their rating (PEGI moreso than ESRB, I believe). They’ve never really explained why it has to cost $3.00 USD every time (instead of an even more nominal sum): but at least under this new policy that’ll end up working out at $1.00 USD per Warhammer title in the trilogy.
The second game in the Warhammer series will be out later this year. No specific release date has been announced just yet.