Not to be TOO snarky, but given how quickly corporate cancels employee labor despite rising revenue, it would not surprise me for other corporate to also cancel "low paying customers" for "high paying customers". Loyalty is beyond dead so cancelling a contract is just a cost of business if they feel the alternative gives more money.
If they canceled a year or so before the con, I could see that. But to cancel seven month before the conference? There's no way they will get a decent-sized substitute in the space before then, so I don't see how this would be anything but a money-loser. Not to mention other conferences might be less willing to commit to long-term deals if they see that the contract can be canceled on a whim.