Yes, Lisa Jackson departed because of differing opinion on certain policies with President Obama and the rest of the administration, but her leaving probably won't have any real affects on the policy. She probably would have had more pull if she had stayed in place where she could affect policy herself.
Though Lisa Jackson's departure will give the department a new pathmaker, it remains to be seen if her replacement will alter course at all. Right now the US is actually in a good situation when it comes to natural gas and oil from shale. The president has allowed more drilling rights than any other president in recent memory. Although I do not believe better energy policy will come from the next EPA chief, I believe we are already in a good situation to become energy independent. For example, the coal industry has some of the most expensive regulations and that is a good thing. Coal is a dirty and inefficient resource that is a relic of another century.
At this point there is little evidence to make me believe that any small tweak could fix the energy policy. Unless we have a major convention and discuss everything that is wrong and ways that we can all contribute and fix it, there is no way that one thing could prompt and put in effect a better energy policy.
The EPA, which stands for the Environmental Protection Agency, is in charge of helping to regulate a resource that is never taken into account by pure capitalism which strives to take into account only the interests of buyers and sellers. If both buyers and sellers are okay with environmental damage in exchange for lower costs, then nothing will protect resources that are used by all humans such as clean air and water. This has nothing to do with better energy policy.