Can diet soda cause elevation in blood sugar?

Not directly, not: sugar. Yet, from observational studies; several years each, people who drink sodas (including diet soda) add more body fat, proportional to amt., than those who don't & ↑ed body fat strongly correlates with ↓ed control of blood sugar ↑es; Diabetes Mellitus, both Types II & I. While the mechanism for diet soda & body fat ↑ may be behavioral or hormonal, good research to clarify this=not available.

Probably Yes: new studies show that artificial sweeteners do increase blood sugar by changing how your body tolerates sugar- makes your body act like a diabetic. The studies are still ongoing, but i believe early results. Diet soda is just as bad or even worse then regular.