Can we install Entity Framework 6.1.3 in Global Assembly Cache and use Entity Framework 4.1 as private assembly?

Question

I have a requirement where in my existing modules are using Entity Framework 4.1 and would continue to use the same for few years and my new modules would use Entity Framework 6.1.3. So I am trying to install Entity Framework 6.1.3 in Global Assembly Cache and continue to use Entity Framework 4.1 as a private assembly in bin folder. All these modules are part of one product. I did the required changes and it seems it is working. But before making a final decision I would like to know if this is a good design decision? What are the pros and cons with this approach?