I think it's expected for people to work on their submissions up until the deadline. I personally know some people working on contest games and I'm sure there's more I don't know about. Pieceofcheese and I were planning to make a game, but then we started making the blind race game for the marathon with other people and that took priority.
You could consider being more casual with the administration if it's too much work. The contests are a nice community event to have, and as a bonus they bring in new game makers to our community.
This is more of a suggestion for the future, but I think 4 and half months is too long. A shorter deadline, say 1 month, would make it more approachable to enter. It's less of a commitment, the pressure is lower, you're less likely to get demotivated or fatigued with your game. And it would be easier to move the timeframe so it doesn't overlap with anything, like the marathon this time. It's also easier to manage for both participants and administrators.