It won't. It'll tell you that you have too many and it won't work. You'll have to go into your iPod options which will be at the bottom of the iTunes window and select the Manual or Playlist syncing. Or you can just delete the songs you don't wanna use first in iTunes. Then, when you're below the max 4.6....gigs, then it'll autosync.
I only wish I could have all the songs I have on my iPod now, stay, and then change to Playlist mode and add new playlists with songs too update. But as of now, if you switched to the playlist option and say you only had 4 playlists with 100 songs, but 1000 songs in total. It would delete all of the other songs off of your iPod that weren't in those playlists. Sucks!
How does one delete a playlist in the iPod. I deleted it in iTunes and actually even recreated it with a different name. Throwing the new playlist on the iPod did nothing. The old one with the old name still exists. So how do you delete a playlist? I checked the invisible playlist file on the HD but it's just gibberish.