The history of MVNOs seems to indicate otherwise. Not a lot of them survive as independent entities; I think because there's not a lot of profit to be had, and most MVNOs are setup where the business is captive to a given operator. You'd need to reissue SIM cards to each customer in order to switch to a new operator, and that's expensive; not to mention some customers have operator locked phones that wouldn't be able to switch, so you've got to develop a plan for them as well.