I think the ending of SPECTRE is left deliberately ambiguous. My belief is that Bond retired and he and Madeleine are driving off into the sunset. This could allow a fresh start for the next actor should Craig not return. I could see him just being on holiday, but the way that Bond throws his gun away it really seems that he is choosing Madeleine over the service. Therefore, I think it's more likely and makes more narrative sense, for Bond to have retired. Then in Bond 25, Madeleine is killed by Blofeld which prompts Bond's return.
I would only want to see Madeleine killed if Craig is in the next installment. If he's not going to return, then leave it with them driving off into the sunset as Bond has done many times before in past installments.
So do I. There's no point in picking up SPECTRE's storyline if Craig's not coming back.
And I personally hope Craig won't return. I love him as Bond, but I like to think his Bond got his long-deserved happy ending.