You can convert your SBD to STEEM and not power up. STEEM can be held like that.
SBD are worth, at face value, only $1 worth of STEEM.
Holding could very well be profitable if the price of SBD goes up....
However, it is a debt instrument that has a par value of what it is worth....if the market decided to listen, you could get hit hard on that....
Just something to keep in mind.