Yes, you can always upgrade to higher edition licenses within one product family at the price difference of the two licenses (at time of the new purchase).
To receive a coupon code for your discounted upgrade order, please log into our website at www.paessler.com/login or write to sales@paessler.com stating the license you are using now, which license you want to upgrade to, and, if available, the Element 5 purchase ID of your original purchase.