The latest news said that the structure is mostly saved. Looking at some aerial pictures (https://pbs.twimg.com/media/D4OFOKMWkAEEHsz.jpg https://pbs.twimg.com

The latest news said that the structure is mostly saved. Looking at some aerial pictures (https://pbs.twimg.com/media/D4OFOKMWkAEEHsz.jpg https://pbs.twimg.com/media/D4OFOKMWkAEEHsz.jpg), it looks like the vault is holding except maybe for the section above the transept area (where the spire collapsed), but it has probably suffered, if not from the collapse of the roof, the heat has probably weakened it. But yes, one or two decades of restoration is a realistic estimation, it's roughly what it took for other cathedrals to be restored (Rouen, Reims) after the World Wars (hopefully Notre-Dame will be in a better state after the disaster)