Worry about the "nobody cares enough" problem long before worrying about the "oh crap, too many people care" problem. User apathy, aka "not enough traction" kills far more startups than inability to scale. Pick the ecosystem with which your company will be most efficient and agile, and cross the scaling bridge if you come to it. We've rewritten substantially all parts of our codebase and key infrastructure 2 or 3 times in the last 8 years. You'll get the pleasure of doing the same iff you have users...