Has there been a change to stop the breaking of the "peg" at debt ratios above 10%?
No. The 10% limit is still in place.
If this is implemented, it will likely cause the debt ratio to increase with the additional SBD production. Have there been any relevant changes, or will it still be potentially catastrophic?
Yes, that is somewhat the intent. The market has signled (through sustaned high SBD prices) that the current 1-2% debt level is not enough supply. This change would allow the market to increase the supply pretty much all the way up to the 'haircut' limit.
With the new market conditions that have opened up around SBD, there is a lot less of a concern with the 10% level being catastrophic. If it starts to get "too close" to that 10% level for comfort, SBD traders will (logically) sell - which will put downward pressure on the SBD price. With enough downward pressure on the SBD price to push it back to $1 USD, this will incentivise conversions again.
Anytime SBD is trading at or below $1 USD, the market essentially has the option to "override" this change by converting an equal amount of SBD each day as gets printed, which would have the same result on the market as the blockchain printing 100% STEEM in place of SBD.
RE: I submitted my first hardfork pull request to the Steem blockchain! (Updates to the SBD print rate.)