At least one research firm thinks in-store mobile payments, mobile wallets usage, is set to explode in the U.S., despite accounts of slow uptake by consumers and crawling installation of NFC terminals by retailers.

The Business Insider Intelligence’s 2016 Mobile Payments Report predicts volume of in-store mobile payments will hit $75 billion this year and $503 billion by 2020. The authors say despite the hurdles of consumer habit and spotty availability, wallets’ benefits to both retailers and shoppers, such as security, speedier checkout process and app integration will boost usage quickly and heavily.

There is skepticism, of course, since all indications have been if not to the contrary, then much more reserved.

“It’s certainly possible that sales could reach that level, but there are many unsolved problems and unknown factors that must be resolved first,” says Rick Oglesby, president of AZ Payments Group and a partner at Double Diamond Group. “As the article states, in-store mobile payments are not yet in full flight.”

A study from Javelin Strategy and Research reported mean mobile wallet usage fell by a fifth since 2013, from 3.7 to 3.0 in 2015. The research firm posits that wallet providers not giving users a reason to pay with a wallet after initial trial. While wallets have been adopted increasingly since 2013, they’re not being used repeatedly, the report says.

One possible wild card in the outlook is the rise of person-to-person payments using phones; the idea is with growing acceptance and use of mobile for apps like Venmo consumers will grow more comfortable with using their phones for financial transactions and be open to paying retailers rather than friends using their mobile devices. Wearable devices may help the cause as well.

Recent moves such as Square’s marketing junket in Portland, Ore., where it blitzed retailers and consumers to raise awareness of its $49 chip reading and NFC terminal, may be the start of what has to happen, education and trial campaigns from all parties—device makers like Apple, PFs like Square, and retailers.