Yes, Focus Blast would still have a chance of missing provided that there are no other accuracy modifiers in play (e.g. Wide Lens). According to the formula for calculating the chance of hitting, Focus Blast would have a 93.1% chance of hitting, meaning that there is still about a 7% chance that it will miss. These are still much better odds than the normal 30% though.
So basically, to guarantee that Focus Blast will hit, you will need to have two Hone Claws set up.