Your only problem, really, is that platies and swordtails are very closely related; in fact most shop bought swordtails are platy/swordtail hybrids, so they will cross breed.
You already have a pretty poor male to female ratio with your platies; you should always have at least two females to each male; she must be a pretty fed up girlie!
Apart from those things (and don't forget you're going to get a lot of fry), you'll be fine, but that will be all your space used up; you won't be able to add any more fish or keep any fry.