Should i trade up my iPhone 4 for an iPhone 5?

They valued my phone at $83. My iPhone 4 is 2 years old. I want to ugrade because i want something faster and my current phone only has 8GB of memory space and i'm a bit short on memory. So if i were to trade it in i would get $83 off an iPhone 5 (priced at $199).Is $83 a good trade up value and should i trade it in now? They say the value may increase or decrease

Added (1). I got my iPhone 4 for free as part of a special offer if that helps

Sell it on ebay or craigslist. You can get $125-$175

I would Wait Because there's rumor that the iPhone 5s or 5c might be coming in mid sept and you might the iphone 5 cheaper.

Ya know what… Mmm…
I suggest waiting for the iPhone 8.
that should give plenty of time too save up for it.
Can you wait for better technology?