Now that Cable and Apocalypse are dead, does that mean the Askani future no longer exists ? Or is it possible that the 2 guys could still be alive ? I remember kiddy-Apocalypse getting shot buy Fantomex and Cable being either disintegrated or devoured completely by techno-organic virus.

Who knows, Apocalypse could possibly be regrown from just a sample of blood with the Celestial's help. As for Cable, the techno-organic virus might have retained Cable's personality and powers like Douglock ?

Apocalypse is alive in one possible future (Messiah War).  As he's one of the X-Men's biggest & most classic foes, then it's unlikely that killing the child will stop Apocalypse from being reborn again. 

As for Cable, I'm sure there's a way he'll be back.  It's been hinted at already in interviews that the arm was left behind for a reason.

But as for the Askani?  It's just one of many possible future timelines.  However, that is in Cable's past... so events that happen to Cable now (ie dying during Second Coming) wont change the actions he did in his past.  That's already happened.  It's all... wibbly wobbly, timey wimey ;)

The Askani reality is not really a future timeline, it's an alternate reality (Earth-4935). And as XK said the things that already happened there can't be affected.

wibbly wobbly, timey wimey ;)