FXB is coming in Frax v2 per governance and community vote of FXS holders. So far, we've discussed the stablecoin, FRAX, and the governance token, FXS, which has control of the seigniorage and revenue flow of the protocol. FXS is similar to ownership/stake in the protocol, not debt which is a separate financial primitive. We have not yet discussed how a fractional-algorithmic system like Frax handles issuance of debt which is extremely important for a complete algorithmic monetary policy. Check this section + GitHub for updates as we release Frax Bond (FXB) specs.