Price was a factor influenced by the market, because niche processors are necessarily more costly.
This can still change very rapidly if there's a market need for such processors, that would fill a new need (notably for safe virtualization): this could start by CPUs made for application servers on the web (which can support a higher initial cost per unit, but rapidly what is available on servers would be used on smaller devices and in home and mobile usages (which now depend more on distributed and cloud services).
We're reaching a point were pure local implementations is not viable (and economically not the most cost effective solution) to get the performance we need in modern applications (which now need scalability and hardware redundancy). Mobile computing also cannot use infinite amounts of energy, they need support from other computing units available via a fast network (but not at the price of security: servers will need to be the first equiped systems to support safe and efficient virtualization)
The traditional stack-based CPUs (with more or less native registers) can be easily replaced, because they can be emulated completely by virtualization, without major impact on existing softwares written for them.
