They shouldn't start casting when the script and all prep is done for all seven seasons. Not a moment sooner than that.
Expecting far too much pre-planning, theyll want to know how well the initial stuff will be received and possibly make adjustments, which they may also be making according to the casting.
Yes, they could do that, but they gotta re-edit the whole thing to make it more woke and more acceptable for modern audiences.
Nope they couldnt do that because they need to re-write it in the format of an episodic tv show that works well.
That would require actual real brains to do, but more importantly, it would be a risk, which you just cannot do to today.
Theres not that much risk with an IP this size they can probably afford two potentially poorly received seasons.