get the sony.
It will work fine for your current goals/needs of a DSLR, and as you said you will change bodies if you get more serious about photography.
Plus sony's (or pentax) are great to have for canon v. nikon shoots. Sony =
(See joeyl's nikon girl )
On another note either canon or nikon will provide similar choices to pentax or sony and have much larger lens line-ups so you won't need to upgrade the body to try different lenses.