This question recently appeared on a Google Opinion sparking the rumour that Google might be launching their own network. Perhaps as an virtual network operator on a larger network however as they have dug in the wiring for Google Fibre is does not rule out the option that they might go to the expense of erecting their own towers.
The best news here is that Google would be charging less than the other networks as you can only use a Nexus device on their network. A master stroke for all those who love a Nexus, and lets face it, there are a lot.
At any rate, this is merely a rumour now. Gauging from public reaction Google might not both. For us little folk in the UK, we would be unlikely to see a Google network for a least 1,000 years.