I'm not sure what your theory is, but a cancellation on the flight the day before is not going to mean anything about your flight today. If you are worried about the cancelation from yesterday being due to low loads and are worried about the same - note that airlines do not cancel strictly because they have low loads. While seems reasonable to think on its own, it isn't when you think about all the things on the backend that get disrupted - crew schedules, aircraft, operations, etc. which would be more of a problem, when, say, the crew and aircraft aren't in the places they need ot be to work their next flight.

As mentioned, 319 and 320 swaps happen relatively frequently. If I don't check in online, I'm often surprised at the aircraft I walk into when its scheduled for one of these.