Apple rarely announces products more than a few days before launch. That makes it difficult to know if the iPod you buy today will be superceded next week. So if you’re looking for the latest and greatest we have to rely on rumors and historical patterns when making our purchasing decisions. This is particularly important for Apple products because many of their products are only released annually and there are rarely price drops in between.
A great resource for making these decsions is the Mac Buyer’s Guide, where you find release history, average product cycle length, and a list of recent rumors. To sum up their current data, the products that are due or overdue for an update are iPad, iMac, and Mac Pro. The MacBook Pro, MacBook Air and Mac Mini are about halfway through their normal cycle, so they recommend waiting on these if it’s not too painful. One thing to consider if you are thinking about upgrading to the iPhone 4S is that if Apple releases an iPhone 5 this summer you won’t be eligible for an upgrade through your cell phone provider for a very long time.
That said, it’s always a great time to buy a refurbished Apple product. You’ll likely be receiving last year’s model but they have great prices. All of their refurbed computers and devices are given a new body and battery, so only the internal components are refurbished. You still get the same great Apple warranty.