It can't, and I wouldn't hold my breath for such a small company being able to navigate compliance for contactless payments. The Pebble does use standard watch straps though, so you could get one of the ones with a programmable payment chip embedded inside.

If that's all you use your smartwatch for, you may as well skip the watch and get a payment bracelet or ring though.

e.g. https://www.curve.com/wearables/

Since this is hackernews, I'll point out that you can use a solvent to remove the card part of a credit card leaving only the chip plus antenna. Then embed in a new housing of your own design.

This. I seldom leave the house with an iPhone, and my Apple Watch with cellular is my primary "mobile" device. I want to leave the Apple ecosystem as my devices age out, and the one thing I would love to have is an NFC ring or bracelet to replace my Apple Watch.

Eric has said publicly this is not happening. Looks like he's making a watch that fits his use case, and since he always carries his phone that's not a priority.