I think the HF20 changes make a haircut on SBD conversion more likely.
The changes to the print limits will allow SBD to be printed all the way up to the 10% debt level cap. This makes it more likely that the 10% cap will be reached. It only needs SBD to be a little above $1 to make 50/50 rewards the better option and for SBD to keep being produced.
In market conditions similar to the ones we have just lived through we could find ourselves in a market where Steem is falling but the SBD conversion guarantee no longer holds. (Imagine if the debt cap was currently at the print limits of 5% for example).
Something I think people should be aware of if they are looking to hold or purchase SBD.