Assured? Perhaps victory was inevitable, but victory might have looked a little different.
The Zeigfreid line was a real bitch and there were a lot fewer people and less equipment to defend it after BOB.
If not for Arhnem or if Arnhem had succeeded there may have been no BOB in the first place.
WWII was so vast and complex that Assured is a pretty big word.
We can speculate all day, tonight, and into tomorrow.
If the Germans did not launch the offensive in the Ardennes, they would have had more armoured reserves to deploy against the Red Army on the Vistula. Our victory in the Battle of the Bulge made it a lot easier for the Red Army to launch its offensive against Berlin.