There are actually many opportunities for priests to get a higher education. Even if you were a Diocesan priest, I’ve never heard of an intelligent one being denied education if it contributes to his ministry. Even with many priests being overworked and in need of help in the parish, most Bishops believe so strongly in constant formation that they’re willing to sacrifice priests for a few years to be further formed.
Also, it’s not every priest who wants to go on to further education. After a minimum of seven years of seminary, most are tired of school, at least for a while. If you are an real student at heart, you have a good chance of continuing your studies, even immediately after ordination.
This is what I’m planning on doing as well. I too love education, and have always wanted a PhD.