Ryanair's present fleet is too big for the airline to go anywhere else than Boeing for new planes.
I don't think so...in fact having such a large fleet of one type can be a hindrance, especially on the negotiation table.
Look at Air Berlin for example, they can approach both Airbus and Boeing and pit them against each other to get the best deal because they operate both type of aircraft!
Say Ryanair ordered 200 aircraft and saved $2m on each - I doubt training crew etc. would cost $400m...
There are dozens of factors involved such as this along with operations, crew contracts etc.