The Lakers game is April 13th, which is also the last day of the entire NBA regular season.
Obviously they just wanted to wait until the season ended. Yes, all signs point to leaving, there's no doubt about that and that's not news. BUT there is still hope, which is why we should all be going to games and the city hall rally to put pressure on both the city to get something moving and the Kings to at least wait another year before a final decision is made.
What really makes me scratch my head is why the NBA relocation deadline is in the middle of the season in the first place. I suppose it makes sense to give teams more time to plan a move, but they can do that behind the scenes without filing. On the other hand, it gives fans a chance to rally support to try to save their team. So who knows.