Apple released the first iPad, the 16GB Wi-Fi-only model for $499, on April 4, 2010. The $499 iPad 2 came out 342 days later, on March 11, 2011.
Another way to look at it is that you paid $1.46 a day for the original iPad before it was obsolete.
We lack the proper sample size for true statistical accuracy, but based on the number of days into a new year Apple released its first two iPads, we can take the average of April 4 (92 days in) and March 11 (69 days in), and guess that the iPad 3 will arrive 81 days into 2012. That would be March 22. That would also mean a 377-day life cycle for the iPad 2.
If you agree to play along with that projection, then the $499 iPad 2 comes out to costing $1.33 a day before obsolescence. That's a relative bargain compared with the first iPad.
But what does that mean for the value of an iPad 2 purchased this holiday buying season?
Let's take Black Friday--November 25. There are 118 days between November 25 and our March 22, 2012 guess for the debut of an iPad 3. That translates to $4.23 a day, or more than three times the daily cost of an original iPad during its life cycle as a new product. For an iPad 2 purchased (or opened) on December 25, that's only 88 days until it's out of date, or $5.67 a day.
An old iPad, of course, doesn't shed all of its value once a new model emerges. Amazon currently lists used, original iPads for $320 and used iPad 2s starting at $439. I wouldn't count on the same conditions for the used iPad market this time next year, not least because there will likely be another iPad in the mix to drive prices down. But considering current used prices, as well as the time of year, the timing looks right if you have an iPad to sell.
I don't really suspect anyone will second guess your fiscal wisdom should you purchase them an iPad 2 this holiday. As a matter of fact, my wife and I just bought one (and I don't believe this house I'm now standing in is made of Gorilla Glass).
Still, we all know that Apple likes a steady release pattern. Anomalies do happen, but going by the numbers, history says you should wait until spring to get maximum value for your tablet dollar.