Yes it is definitely legitimate. The initial part of the process is that you complete the form by the cut-off date so that we can calculate your upgrade price based on your existing purchases. After that, we will send you a unique coupon code which you may use to purchase the upgrade at the discounted cost.
The cost of the actual full priced packages are mentioned on our
checkout page.
Upgrading during this time will mean you get all current and future themes for one set price with free lifetime updates included before we soon implement an annual subscription fee. If you choose not to upgrade, you will still continue to receive free lifetime updates for your existing purchase, but any future upgrades or purchases will be subject to the annual fee.
I hope this explains it better. Thanks.