I've been out when the carriage road is a pond and Uberfall is a waterfall and you can always find something to climb. The question is, are you looking to roll up with a list of "three star classics" and never deviate from those seven climbs you picked out for the weekend? Most people I see complaining about there being "nothing to climb" aren't willing to just climb what is open, dry, whatever. I am not saying there is anything wrong with this approach, but it will cause you to be disappointed quite often and miss out on perfectly fun days on the rock.
As for trees blocking the routes, I'm sure you can scramble over a few trees, but if you can't, I find it unlikely that trees will be blocking all 600 or so routes.
If the visitor center never even lost power, I would bet you can find enough to climb to fill up a weekend.