The entire amount of bLUNA deposited as collateral earns a staking yield. It isn’t the full 11.4% though. Some percentage is used for ANC buybacks and some % goes to validators. This yield currently is not enough to cover Anchor’s deposit interest rate.
There has always been plans to introduce bETH, bATOM and other POS coins. The problem is that if the bonded POS coin has a higher staking yield than bLUNA, a borrower would expect to pay a smaller explicit interest rate as he is foregoing his staking yield. We should not expect other bAssets to produce significantly higher effective staking yield + borrow interest rate relative to bLUNA.
A revenue stream outside of Anchor seems like the ideal solution to this problem.