OK, that makes the picture much clearer.
It's probably true that you would "outgrow" a larger board (perhaps a Rio or a Go) in about half a year, but getting a board as small as the Kombat 122 is going to make your learning curve much more difficult than necessary.
I hope that learning to windsurf on the Kombat TufSkin 122 will not prove so difficult that you give up on windsurfing all together.
Are there any WS schools in your area (or dealers with basic skills lessons programs)?
This would allow you to get past the very basics (which will be alot more difficult on the Kombat Tufskin 122) on a larger board, and then you can take your newly developed skills and balance onto the Kombat 122.
It's not that the K122 will not float you or anyting major like that, it's just that it will be significantly more "tippy" and much harder to learn the basics on, than say a Rio M; Rio S; or one of the larger GO boards.
Sorry to "rain on your parade" here, but I'm not sure your dealer is being completely up front of the skills needed to sail the K-122.
Your Opti and Laser skills will transfer (sort of). You will know how to read the wind direction and how to look at the water for signs of significant wind increases or lulls.
Beyond those two "skills" windsurfing will be pretty much completely new.
I sailed all types of dinghies since I was 8 yrs. old, but when I first got on a Windsurfer One Design at the age of 30 something, I was completely lost and had to swim the board back to where I started.
Being a persistent kind of guy, I kept at "learning to windsurf" for quite a while before I actually was able to really say I had the basics mastered.
I had no access to lessons, so I had to learn everything the hard way.
I have taught windsurfing all over the USA, in Thailand, and a little bit in the Caribbean
and while I see those students who have sailed dinghies before as having some advantages, the learning curve is still pretty steep.
Hope this helps,