I asked for some field reports from the season-ticket holder relocation event held Wednesday, and I not only received one, I also got the 12 photos you see in the gallery above. You can clearly see all the seats marked off for current season-ticket holder relocation. While I have no specific evidence of this, the marked seats should also give you an idea of how many seats the Cubs will have for new season-ticket holders, because every season-ticket holder who relocates opens up an identical number of seats that can be purchased by someone new.
The Cubs have had events like this in January for people they call off the waiting list to choose seats; I have no reason to doubt that they'll do this again this coming January. This might be the last season this happens for a while; presuming the Cubs can actually begin construction on the renovation project next winter, during those construction offseasons these kinds of events will happen online.
Speaking of offseason work, you can also see in the photos some of that work going on in various parts of the ballpark, particularly along the left-field line. This isn't related to the Wrigley renovation plans; maintenance work like this is done pretty much every offseason.
Post a report in the comments if you were one of the people who attended Wednesday's relocation event.