That is a good point, getting to the debt limit shows we are efficiently removing Hive from supply (ie. good rates of Hive per HBD).

I am just a little concerned of what will happen when we get there, with the cessation of HBD printing it will be harder to maintain the peg, and similarly we may not be able to funnel excess HBD demand into price of Hive.

The debt limit was introduced by Dan at the very beginning to limit the risks associated with creating debt on the blockchain, it was expected that SBD would always be a small proportion of Steem overall. Excess demand for HBD should funnel into Hive increasing its price, however, there is no economic law preventing demand for HBD to exceed demand for the token acting as collateral. It could be a precarious situation if it did.