Dean, I don't think people are talking about problems with the Enter key. The problem is one that affects people playing with the mouse, where a careless click that misses a letter can submit the word.
There are currently three ways to submit a word: the green arrow, the Enter key and clicking on an unoccupied spot on the "X". When people suggest words should only be played via the green arrow, they're not even thinking about the Enter key. So don't worry, keyboard mode is not under threat.
Incidentally, I'm experimenting with a refinement that will submit the word only if you click on the area a letter has just moved from. Effectively you could submit the word by "double clicking" on the last letter. (Except it's not really double clicking because the letter will probably have already moved away by the time your second click happens.) So if your next click misses the letter you were aiming at, it won't do anything. The green arrow and the Enter key will still be available.