If you wait for Gamescom and there's a price drop, the value of your current PS3 will go down DRASTICALLY. If you're at all worried about having so survive another YLOD, or any other hardware malfunction for that matter, it may ease your mind more to just get the latest and greatest model. My advice is to sell your current PS3 as soon as possible (on eBay or Craigslist, NOT GAMESTOP), and then pick up the redesigned, pricedropped, bigger HDD'd, slimmed and trimmed model after Gamescom. The only downside to this is plan is that you may have to wait a bit for the new model and not have a PS3 in the meantime (unless you have a buddy that has one).
Or just get yourself a bigger internal HDD, like some other people were saying. Good luck with whatever you choose.
