Hello there, I'm just a newbie here so please bear with me. I'm 1000% sure it's a compatibility problem between iOS 7.11 and newer models of iphones plus ipod touches. I've encountered the same annoyance many times- ipod touch 5th gen syncs perfectly for an entire month then gets stuck on the dreaded "preparing to update". Please don't hit me for saying this, but the best option is to wait: it once took me literally 15 minutes to get 2 bloody songs on my device- it WILL update eventually. Still, if you (as a perfectly reasonable human being) can't accept that, try re-installing itunes- this has worked for me in the past, but is fairly sporadic, only effective 60% of the time. Finally, I have a hypothesis that has to do with album art- I once sat my arse down and noticed that the "updates" usually ends with a painfully slow "updating files". I also noticed after running some experiments that songs WITHOUT album art sync much, much faster. I highly suggest you try syncing your tracks without the album art, then fixing it on your device, as inconvenient as it is.
I sincerely hope my advice would be of use. Sorry for the useless rambling.