Is vaping a gateway to smoking?

No. As vaping rates have increased over the past decade, smoking rates have reached record lows across all age groups. If vaping led to smoking, smoking rates would be increasing, not declining. Therefore, there is zero evidence that vaping leads to smoking. Read more here. Sometimes sleight of hand may be used to attempt to demonstrate a Gateway effect

Additional reading

How not to be duped by gateway effect claims by Clive Bates

Gateway Effects: Why the Cited Evidence Does Not Support Their Existence for Low-Risk Tobacco Products (and What Evidence Would) by Carl V. Phillips