The availability is quite good:

Surprisingly it's allegedly fuller at the front - so perhaps they're anticipating a lot of missed connections or cancellations, or maybe they can move people onto the earlier A380.

I assume that you're a Blue Exec Club member as you hadn't selected a seat yet - keep checking throughout the day as there does seem to be some availability and an upgrade is more likely than being denied boarding.

Edit: Blocked seats at this stage tend to indicate seats that have been allocated but not yet taken by someone checking in - maybe they won't. However, as there are truly empty seats further forward, then it's likely that either you will be upgraded due to a full economy cabin, or someone else will and you'll have their seat (which is probably still good for you - if they're a Gold member they probably chose a good seat before vacating it!)