While it is true that a 32 bit application using a bridging app can access 64 bit plugins and these can have large "streaming" libraries using samples from the hard drive, when using plugins that use RAM (ie modelling VSTs for example) you are STILL restricted the the max RAM of 4 gig by the 32 bit OS.

Now usually this is no great issue, unless you start stacking several plugs. Then the limitations of a 32 bit app and OS start to be noticed.