I agree that Firbase is a ool option and probably safe as they recently took steps to lock it into the google account. Someone will inevitably say google kills projects often, but they probably won't kill this.
Alphabet's strategy seems to be yo onboard new developers and get into mobile.Firebase is a good way to begin that pipeline allowing new devs into googles ecosystem and controlling how tags work on websites by creating their own library and pushing people in.
Why did parse fail though? Seems like a good strategy for Facebook.