I agree that it's not scummy, but don't be here running defense for the developer and making up reasons for why something is or isn't viable.
Of course, the developer is under no obligation to hand out Steam keys, nor has he hasn't said anything about it yet. But I think that most early supporters (myself included) would appreciate an acknowledgement of said support.
It's pretty simple: I bought the game twice already, I am not buying it a third time, but if I were given the Steam version, I would be more inclined to support this developer in future.