I carried around two 17" PowerBook G4s in one laptop bag for a few years.
I'm typing this on my new (couple of weeks) 32 bit MacBook Pro 17" (A1151). My 17" PowerBook G4 (A1013) is playing music on the table in front of me.
I love the 17" PowerBooks so in my need to get an MBP I got one that looks as close to the Albooks as possible.
Both the PB and the MBP do everything I need and I do not consider 17"s to not be portable, as I take my 17" PB to work with me every day.
All of that said, Apple is on a smaller, lighter, thinner design kick right now and I do not believe we will see a return to the 17" form factor any time soon.