License Upgrades

If I start with making a game, which turns out to be absolutely amazing using Visionaire, but only using the Indie version, by later decide I would like to become rich from it, and hence upgrading to professional version...
Is it possible to upgrade my Indie license to Pro, without having to pay the FULL amount in buying a pro license.
I don't like the idea of buying both, but as you will understand, an idea is not worth paying a full license if no money is to be made. Thanks

No, you don't get a deduction from the professional license. Both of the indie licenses allow you create, work on & release as many indie titles as you like (digitally).

The professionally license does come with the indie license, but the fundamental difference between indie & the professional license is that you can only use the professional license on a single title (game) that you want to publish. Both licenses are commercial, so don't worry about that. You only need a professional license if you have been commissioned (hired) by a third party (such as a publisher, company or individual) to develop a game for them &/or if you intend to release your game as a physical boxed copy in retail stores such as Game, Grainger Games, CEX, etc (listing some uk stores I can remember off the top of my head).

If you do decide that you eventually need a professional license or mobile license (which is also per title), then you can purchase one at a later date, as & when you need it, other than that the most you will need for testing & development is an indie single or indie multi license (if you are working with multiple developers on the same project in the same location, say a studio or your bedroom, or whatever).