If the 002 is working for you I can't see much of a reason to switch. Depending what you do more i/o could be useful though so adding a few converters by ADAT would be one way to go.
At the 002 we had in a previous studio the ADAT unfortunately stopped working so wouldn't really recommend it for stability...
Plus, if you're recording in 88.2 or 96 khz you're reduced to only four channels on your ADAT and usually some trouble setting everything up.
What to upgrade to is of course dependent on what you need and how much you're prepared to spend... If I had the money I think I would go for 8 or 16 channels Lynx Aurora interface. Can be fitted with FW if you like or if you have a stationary computer connect to a PCIe card (any AES/EBU interface really).
You'll need to get mic preamps though which adds even more to the costs but could really be worth it if you want to step up a bit.
http://www.lynxstudio.com/product_detail.asp?i=50
Mytek has a similar product. I've only tried their 2 channel ADC but it was great. Very transparent if that's what you're after. A bit pricier than the Lynx though... And you'd still need preamps of course.
http://www.mytekdigital.com/products/8x192adda.htm