What If the Asteroid had Missed? 

The asteroid hit at the end of the Cretaceous, killed off the dinosaurs (birds are the only survivors) and gave mammals the space to thrive. THIS ARTICLE by a Bath academic speculates on what would have happened if the asteroid strike had not happened.

Was the arrival of intelligent tool-users inevitable? And would they be dinosaur descendants. 

Probably not. Sauropod dinosaurs had a long history of being huge in body, small in brain. From the Jurassic to the end of the Cretaceous this held true.

Carnivorous dinosaurs had a similar history - big bodies, small brains.

This recipe may not have been a precursor of intelligent tool-users but it would have been enough to stop mammals (especially us) from becoming such.

Brain size versus body mass for dinosaurs, mammals, and birds. Nick Longrich

The development of mammals was not inevitable. Monkeys in South America remained as monkeys. Primates in South America never (even after at least three starts) develop large brains - they went extinct. 

Only in Africa did we emerge.

This is inevitably a very speculative article, but well worth reading.