Question

He worked really hard and thus.... To be promoted

Answer 1

he worked really hard and thus going to be promoted

Answer 2

The answer is:  He worked really hard and thus deserves to be promoted.

This sentence indicates that the person about whom this statement is made is a very hardworking and it has been acknowledged by his seniors.

So as an appreciation he must be promoted. This sentence has two parts. The second part is consequences of the first part of the sentence that he worked really hard.