Although I am not at all a fan of Ace from the beginning (I just like his DF, its fucking awesome) I felt bad for him when I read the latest chapter because his life was nothing but a tragedy. So I got kind of nostalgic and started going through chapters from Shaboady Archipelago and I have a slight feeling that Portgas D.Ace could be alive. But I am not really sure about this, next chapter will definitely clarify if Ace is dead for sure or not. But some facts kind of hinted to the fact that Ace might not have died afterall.
1. Why was Kuma in Shaboady during that Tenrobityu incident when there were no orders from Govt.?
Ans: For the first time, it was publicly announced that Ace is going to be executed. Disco-Doflamingo, again on the same day converse over phone and Doflamingo tells him that he has been called to a Shichibukai assembly related to Ace's execution.
So it is highly probable that even kuma came to know about it the same day.
So Kuma realises that if Luffy comes to know about this, he will definitely go to Marineford and will get killed for sure. So he goes to Shaboady to send the mugiwara crew to far off islands.
2. What did he tell Rayleigh?
Ans: That Ace is going to be executed in 10 days and that "Ace-Luffy" are brothers. So I need to send him very far to keep him safe. Rayleigh reacts saying, "Should I believe that nonsense?" because it was posted in papers the same day and it is highly likely that he does not know of it.
3. Why should Rayleigh come and save Ace?
Ans: If Rayleigh knew that Ace was Roger's son from before, Kuma's conversation let him know that he was going to be executed. So he would come to save Ace by default and he had like "7 idle days" after coating the ship to go to marineford.
And if he didn't know, doesn't really matter because Ace's execution has become a famous issue in Shaboady. So he would have heard it from some-one or watched it live himself. Its just that he would have less time for preparation now, but he would put his life on to saving Ace.
So I have a strong feeling that Rayleigh is going to turn-up in Marineford with coated-sunny and save Ace the next chapter. Now don't ask me from where he is going to get expert doctors and stuff but anything is possible in OP world. Ace might become a cyborg…Who knows??
Remember one thing. In one of the chapters, Garp says that it is too tough for Marines to take on "Two-Legends" at the same time. So I guess Rayleigh's entrance is going to turn tables of this war. It is also apt because "Legends" of previous era should lay a path for the "New Era."
Also, Rayleigh is going to play very minor role in the future and his major role has to be this saga because the new-era is starting. And if Rayleigh did not turn up because he did not know that Ace is Roger's son, he will eventually come to know of that fact sometime soon. What kind of a fucked up legend is he who could not save his Sencho's son.
If both WB and Ace die, Ace's death basically overshadows WB's death and it would seem as if ace laid path to new era. He bloody belongs to this era. Then how the hell can he lay path for a new era??