If the price of Pepsi decreases, all else held constant, then we’d expect to see a consequent shift of the demand curve for

There will be a shift in the demand curve

Explanation:

A shift in the demand curve is influenced by many factors. For example, the shift happens when the demand curve moves either to the right or to the left. Several factors contribute towards the shift:

The product becomes popular. There is an increase in the cost of the goods. The price of the complement goods and services increases. There is a rise in the incomes generated.

All the factors above contribute to a consequent shift in the supply and demand curve.

The demand curve itself should actually move. Instead you would be moving along the curve. Your question is incomplete but the information given would result in a shift to the right on the demand curve. In other words, quantity demanded for pepsi would increase. (There would be a shift to the left on the supply curve.)