Thankfully, the new, fourth generation iPad comes with a beefier wall charger rated at 12 watts on the output. The iPad mini has one of these as well. With the inclusion of the more powerful accessory, iPad owners shouldn't be experiencing any charging issues. In fact, if they happen to own any of the previous iPads, they can get the new 12W adapter and use it with them as it is fully compatible. Moreover, it is able to charge older iPads faster, as it turns out. "We don’t have an exact percentage of how much faster it would charge but you should see an increase in speed.", Apple said to 9to5Mac.
So if you plan on sticking to your current iPad instead of getting any of the newer models, you might consider getting one. The new 12-watt power adapter is already available from the Apple store and it is priced at $19.
source: 9to5Mac, Apple