Yeah like they already mentioned, they don't know if all Unity features will be available and how the performance will be in the end.
I didn't forget the "Flash" part, i personally don't like Flash either. But what i mean is, it seems like a lot of companies actually want Flash for their mini/indie projects. I often got clients asking me if i can do it in Flash instead of unity web player (especially since almost everyone has a flash player).
So i'm sure many companies will switch to Unity then since they can still keep creating their flash games + release it for iPhone, mac, pc, android, etc with a single click as well.
Means more clients = more money for me 8D