Cut avocados in half lengthwise and remove pits. Score flesh into a cross-hatch pattern and, using a large spoon, scoop it out. Place the avocados in a medium bowl. Add jicama, radish, and pumpkin seeds.
In a serving bowl, whisk together sour cream, orange juice, lime juice, sugar, and olive oil. Transfer vegetables to the bowl with the dressing and toss well. Season with salt and pepper, garnish with the pomegranate seeds, and serve.