We will be there June 6-15 and had the same concerns you have. Especially after reading some reports of the Grainger convention being so large that the pools were shut down to regular hotel guests
After freaking out about it in a major way and posting this same question, I was calmed by the more level headed folks here on the Dis.
The people attending the convention are there to do convention meetings and business, meaning they aren't at the pools or on the bus-leaving more room for us
Also when I checked my dates, I found that I could still book for any category room and with the discount being offered right now, meaning that they aren't sold out. If there were thousands and thousands of convention guests I would think they would have those rooms on hold.
I've been so looking forward to CSR that I don't want to switch my plans no matter what convention is there. I can't wait for June