Your situation will vary depending on how much your early termination fee is and how much money you can get for your current smartphone.
3. Special trade-in deals
It's possible your wireless provider may offer special deals and discounts. Verizon explained to me that the full cost of the iPhone 5s will be $550 without a contract (I've tried to corroborate that, but since it's not available for pre-order it's hard to find official pricing information aside from what Apple has posted on its site), and that they are offering me a $100 upgrade ineligibility discount. Basically, they won't let me upgrade early, so they're throwing me a $100 bone.
So, the cost of the iPhone 5s after the upgrade ineligibility discount is $450, and I can trade my current iPhone 4s to Verizon for $200, and I end up paying $250 out of pocket.Or, I could sell my iPhone 4s myself (see above), and get more money for it and spend even less out of pocket for the iPhone 5s.
The $250 is $50 more than the $200 price with a new contract, and it's probably more money than I'd end up spending selling the iPhone 4s myself and paying the early termination fee. The advantage, though, is that I get to keep my existing number, and as a bonus my upgrade eligibility doesn't reset, so I'd actually be eligible to upgrade again with a new contract in just a few months if I choose.
You could just wait.
If you got your smartphone in the last year, odds are fair that it's good enough as is, and there is really no reason for you to jump through hoops to rush out and get an iPhone 5s.
If you got it more than a year ago, you're contract will be up before you know it, and you can go get an iPhone 5s if you choose without having to go through all of this hassle.
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