At $1, yes it is a riskless bet in some sense.
As things stand now, HBD should usually trade at just above $1. That makes buying it not quite riskless. I'm not saying that's what happens, but that's the behavior that would be economically sensible if pegging were working.
I would like to adjust the fee part of blocktrades proposal for HIVE->HBD conversions to apply to both sides. That is, X/2 percent conversion fee on each side, instead of just the X% (proposed by blocktrades to be 5%) on the HIVE->HBD side and no fee on the other side. In effect, this would make HBD convertable into slightly less ($1 less fee). In that case, HBD would be more likely to trade around $1 where the risk of gain and loss is more balanced, instead of slightly above $1 which is what I think would happen now (if the upper end were successfully pegged). Since this isn't a priority it will likely wait until some future hard fork and for the time being HBD will likely tend to trade a bit above $1 instead of around $1.