Wrong, wrong, wrong... Apple could limit some iMessage features on Android if it's so scared or sell it for $1 per year. Messaging is huge, bringing iMessage to Android would help Apple get much more attention and boost sales in China alone. Apple would win much more than it could possibly lose.
They already do... it's called SMS/MMS.
Geez guys, you'd think that you couldn't msg people on Android phones through the Message app. So what if the bubbles are green and not blue. What more do you need? Stickers, SFX, etc.? Just send your msg (or pic) and move on.