My computer ate my post. Damnit, lets try this again.
The Question: Can a MMORPG player migrate successfully to RTS?
The Answer: A strong resounding yes.
Think of an RTS like playing a mage in wow. Both are a bit of a juggling act. The one mistake most first-time RTS players make is to focus on one thing and forget everything else. Building your base up is usually what you stop on. Remember that you have more to manage than just point and shoot. You have to worry about defense, offense, and base management all the same time.
If you can play one game you can play another, the question is just how well? I had a larger, more in depth post but as I said above, it got eaten.