I think it really depends on your cats, and not on the size of your apartment. Some cats wouldn't be happy with others around even if they lived in a mansion with their own butlers and separate entrances for all.
My own experience: I have four cats in about 900 sq ft, and they get along very well. Connor occasionally has issues with Boots getting into his personal space, so they sometimes get into little paw-batting spats, but it's nothing major, and we don't have any litter pan issues, fights, or anything like that. They have their own bedroom in which they are locked when we are away, and it has a nice window so they can dream about stalking birds.
However, Connor lived with several other cats in a small-ish apartment for the first six months of his life, and he's very social, and loves the company of other cats. The Sharks have been together their whole lives and would hate hate hate to be without other cats. Their attitude is not really typical of a lot of other cats I've met. My sister's cat stayed here for almost a year and she was NOT social and did NOT like the company and her issues with other animals created so many problems in the relationships between all my other pets.
You need to ask yourself if your cats will thrive with lots of company, if they'll just tolerate the other cats, or if they'll outright hate having to live so close to other cats in a small space. If you don't think that your current cats will absolutely thrive with extra company in your current apartment, it's probably best to wait until you move somewhere with more space. If they are super-social and love company, go for it.