I have no idea, but second layer networks have much different properties than a custodial paypal service has. In terms of USD vs BTC spending - I imagine a lot

I have no idea, but second layer networks have much different properties than a custodial paypal service has. In terms of USD vs BTC spending - I imagine a lot of people will want to spend USD, and BTC will serve as a store of value and backing asset. USD is possible via stablecoins though.