Honestly I think we'll be fine. If the services are worth something then people will be willing to pay for them. Newspapers, magazines, email, satellite radio, navigation systems etc. all existed (and were very profitable) well before online advertising became what it is now. We might even be better off that way.

FOSS and paid services will rise and shine.

For navigation to a known address, OSMAnd works great. Google Maps is better at search, particularly for commercial destinations, and has a slicker interface. For everything else, particularly navigation off road (on trails or otherwise) OSM excels. OSM has much more detail than Google Maps for things like parks and trails, frequently even having the locations of water fountains (this has saved my ass a few times.)

I guess my point is the alternatives to Google Maps aren't perfect but they have a lot more to offer than many people assume. When I drove across Canada, from Ottawa to Anchorage, OSM never let me down. It's a viable alternative.