Compare 5 years ago [this list is valid for back in 2005 as well, only difference is that I had a different iPod model then] when I had a non-smartphone, an iPod [which I don't have simply because the HDD died and I never bothered trying to replace it], a DS [which got replaced by my 3DS, and the DS's screen got cracked], and that was it. 3 devices. And going back a little further, I had only a Palm m100 and a Game Boy Advance.
I'm likely to get more devices rather than fewer, even as their feature-sets converge -- all of my 5 current portable devices play MP3s, 4 of them can play games [all but the standalone MP3 player], 3 can do computing tasks [homebrew enabled PSP, phone, netbook], etc.
Hell, I'm probably going to get an e-ink based reader soon [much nicer to read on than a bright screen], I might get a tablet for things that my phone is too small for and my netbook is too clunky to just pull out for, etc. And the game consoles in my list will likely stay there or increase [for games/systems that can't be emulated, games that are exclusive to a system, etc]. If something neat comes out for it and I have the coin to spend [probably not, haha], I'd probably get a Vita too.
If the phone had 20 hours of active battery life though, I'd be a lot more tempted to drop some of the other devices. But with enough pockets, it's not terribly inconvenient to have all these things on your person, larger stuff would get stuffed in the backpack.
And last but not least, even these generalized devices still fill a niche for me. In my case, the netbook is for running normal PC programs on, the phone makes calls and has 3G internet, the PSP plays Wipeout and whatnot, the 3DS plays Pokemon and whatnot, the MP3 player plays music and lasts all day doing so, etc.
If I took more pictures ever, I'd definitely carry a standalone camera since the phone camera sucks and the 3DS camera is the worst possible thing that still captures an image.