The Raspberry Pi 2 is a serious upgrade over older versions, and that means you'll need to update a lot of your software to use it. You could make a whole new SD card, but if you have old projects that you don't want to lose, The Pi Hut shows off the upgrade process in Raspbian.
While you're waiting for your Pi 2 to arrive, you can upgrade Raspbian using your A+ or B+. Just pop into the command line and enter these commands:
sudo apt-get update sudo apt-get upgrade sudo apt-get dist-upgrade sudo apt-get install raspberrypi-ui-mods
That's it. After a little bit of time, your micro SD card will be ready for the Pi 2, and all your previous settings, downloads and everything else will still be on the card.