It's only a gateway drug because criminalising it made it part of a drugs sub-culture where other drugs were bought and sold and hence dope users come across them. There's no logical reason why a dope user should gravitate to heroin any more than an alcohol user. Indeed, these days you can say alcohol is a gateway drug to cocaine, because people who've never smoked a joint will routinely be introduced to cocaine in pub toilets.No chance it’s a gateway drug for harder drugs further down the line.
Won’t happen for some but most people with drug issue started on weed.