Large 3D MMORPGs are almost exclusively written in C++, with something an embedded scripting language that handles changable game logic (for instance, mini-quests). However, a MMORPG is, by definition, a massive undertaking, and learning C++ is a mere minor part of the knowledge and experience you need to amass to tackle such a project effectively.
So my advice would be to get more experienced at programming as well as learning C++ (two activities that are not mutually exclusive). Perhaps post up examples of your code, and get people to suggest improvements.
Edit: As a postscript, I should add that the choice of language depends very much on the scale of your MMORPG. If your game is 3D, use C++. If your game is going to have many thousands of players online at the same time, use C++. However, if you can get away with using a higher level language, in my opinion it would make development much, much easier. The question is whether you can get away with the speed decrease.
