S3 owners - Is it worth upgrading to S4 or should we stick it out till next year? Here's my theory. I am currently a proud owner of a Samsung Galaxy S3 and it is by far the greatest cell phone I have ever purchased. There is literally nothing about this phone that I can complain about. 

Because of this, I don't really see upgrading to the S4 as being necessary *but* I think I might actually be able to upgrade for free. If I sell my unlocked S3 on eBay, I can get ~$300 for it. It's in mint condition and comes with some accessories as well as the original packaging so there isn't a doubt in my mind that I can sell it easily. 

The upgrade to an S4 is only going to cost $150 so I'd actually be *making money* by upgrading now. If I wait for the S5 to come out, my S3 won't be worth nearly as much anymore.

Bottom line, even though I'm completely content with my phone as is, it literally pays to upgrade now than wait it out. Good idea or am I missing something here?