What IF ..*SPOILERS*
What if L never died. Say like he joined the SPK with Near ,Mello and Mat. What if light yagami was spying on them , and since L told light before that He has concluded th Misa Amane is the Second Kira. So , Light tells Rem to come with him to his computer to hear what the SPK are discussing. Light knows Rem will get mad and she does. She knows she will have to kill L and Watari , because light set things up like that. She kills both of them. Mello acting on his emotions kidnaps Misa Amane(instead of Takada). Misa kills him. And since Near would send his men to get misa , light killed her. Near concludes that Light yagami is Kira since he would want to keep her quiet. Near and Light meet like in chapters 100-107.Near states that this time it was L that helped him win. L knew that the cameras were in the SPK building, and purposely said that Misa is second Kira, knowing that Rem and Light were listening. L set that up so that he could get killed knowing that Mello will kidnap Misa and that Mello will get killed. L also knew that Near would send his men to get misa and Light would kill her, giving Near the evidence he needs to conclude Light is Kira.
That is my what if. Feel free to post your comments, and your own What ifs
It doesn't matter. He died and Light lost. Get over it.
L didn't even consider the possibility of Near or Mello taking over for him. Remember, he named Light as his successor.
I don't think L would plan his own death. He's not weak enough for that. The only person who was subjected to that was Mello, and even though Near says that Mello realized that he needed to sacrifice himself, I still say that Near manipulated Mello into doing that. L would do his routine pulling the truth out of his ass and start planning the next step. Why would L leave the job of finding Kira to unknown successor/s?