Absolutely, besides even Imacon scanned 4*5 files are about 450 MB... which quickly turns into 1.x GB after adding a few adjustement layers in PS.
Anyway, Vista will be here soon, 64 bits power to Windows and no limitation anymore.
Vista x64 needs to be much better supported than XP x64 is if it is to be successfully used for large-scale digital imaging. For example, only Gretag Macbeth (as far as I am aware) has released drivers for XP x64 - no other color management system is currently compatible.
Windows Vista, in both 32 and 64 bit versions, may bring new color management hassles with its revamped color management subsystem. Whether hardware manufacturers will respond with updated drivers, and in what timeframe, remains to be seen. It could be that Vista will have compatibility with legacy drivers; I am planning to try the beta 2 of Vista that is coming this week to determine whether current drivers will work.
Of course, until Adobe updates Photoshop with full 64 bit support, the benefit of more than 4GB of RAM will not be fully realized. I haven't heard anything on this, but suspect that Adobe won't be doing this until after CS3 - which is somewhat understandable if slightly annoying, because now only a very few Powermac G5 users and even fewer dual Opteron or Xeon PC users use more than 4GB of RAM.