If Apple offered iMessage for Android, I would switch to Android tomorrow. That and consistent, timely iOS updates are the only things that have kept me on iPhone for the last 2-3 years. I really, really want out of the walled garden but my entire extended family and most friends use Apple devices and I would be completely out of the loop as I couldn't convince all my friends/family to install/use something like WhatsApp. Heck, many of my family members would be completely flummoxed if they tried to master a new and different messaging app as they can barely navigate iMessage (LOL).
I understand why Apple doesn't release iMessage for Android - it's to keep people like me from switching away from their very overpriced hardware. There would be some benefits for Apple in making iMessage universal, especially with the new iMessage payments feature in iOS 11 and sticker packs, etc., just not enough to counteract the loss in hardware and app sales for those iPhone users who would then jump to Android.
I really don't care about iMessage. If my family and friends uses iMeesage then that is good for them. They can text me like they would text others. The only thing I care is WeChat and thank god it is cross platformm I hate wall gardened OS. I have no interest in ever going back to iPhone.