From what I can tell, I think there will be a lot of open rooms. As one who booked OGT, I've been watching the rooms available to book (i.e. ones you can actually select in a category) to see what might get assigned.
As of this past weekend, there were only 10 oceanview rooms. That's not a lot, however, if you look at the verandah rooms, my estimate has it over 200 available.
The process is not easy, I actually created a chart with each room that is listed in each of the verandah categories and then went on
DCL's site and input every single room (exept 5A and 4A as there were too many rooms to go through - maybe by this weekend I'll do those).

Anyhow, DCL only lists a maximum of 8 rooms when you go in to select a category, but you can enter all the other rooms. I know that 5E only had 1 room, 5672. For 5 B, C and D, and 4 B, C, D, and E, my count was well above 160, and that was NOT with the 4A's or 5A's like I said. But those alone add a minimum of 8 each, so another 16 bringing us to around 175 +/- for sure. I would have to think there is at least 25 more rooms between those two categories. Heck, there are a good number of 4E's for this Saturday's sailing.
So, it looks like we may not be as crowded as some cruises. I'm thinking a lot of people don't travel that late in summer and I think the FL kids are back in school by the time we sail. So if we figure 200 rooms with an average of 3 per room, we could be looking at sailing light by 600 passengers. Great, the line for the AquaDuck may only be an hour long.
I'll try to post tonight the amount of rooms in each category that I showed available (just double checked the 5 B-D and 4E's this weekend).