Leaving aside the evac or not situation , and it does look very scary indeed with the whole wing alight if iwas a regualr SQ pax I would wonder about he diversion back to base.
it does seem quite common now to return to home or convenient airport rather than land asap. With the smell of fuel in the cabin shouldnt one of the flight deck come back for a nose around?
If there was clear evidence of a fuel leak surely a land asap is the wisest course since had this inferno broken out at FL170 everyone is dead for sure and it seems mere chance that airflow kept the flames away from the engine -if more and more fuel leaked sooner or later its going to find something hot . Is there a bit too much trust in the airframe at times or a bit too much emphasis on what it will cost to hotac 300 pax , provide a substitute plane and then recover this one.
it does seem to me to be a lucky escape but more from the diversion point of view than slides or no slides