I can see this a good and bad thing.
For
GW:
It gives them 12 dates spread across the year in which people will flock to play the tournaments. Maximising thier use of the Warhammer World throughout the year. (think this is the main driver for this change).
I'd expect every seasonal tournament to still be fully booked out; if not at least 90% capacity.
Reduces Admin, having to determine who has qualified and replace people who drop out of final for personal reasons.
For Players:
Will likely get more newbie tourney players entering as their will be less of a rush to get to a certain Heat.
Meanwhile hardcore tourney players could book to attend all 4 games each year.
Or spreadout which Season they play each game (
WH40K in Autumn, Fantasy in Spring, maybe dabble in War of the Ring in Summer).
Less chance that you will face those foreign teams unless you pick the Season they choose.
I must admit that the Heat round of the tournament does put a lot of pressure on your games; you don't need to come top but you need to get high enough to get in the top 40.
Now just the normal pressure of winning my games.
Will miss the feeling of a "Grand Final", but I think it is a good move by
GW (back to how it was about 8 years ago - but more often).
Maybe
GW should take the top winners from each Seasonal to play in an "Invitational" Grand Final like they do in America?