Rebranding
Corporate rebranding is a high-cost and high-risk exercise.
Ryanair as a brand is recognised all round Europe and a good chunk of the affluent world. If one person is associated with Ryanair, it's MOL, rather than anyone in the Ryan family. Having Ryan in the corporate name probably has a neutral effect.
Potential reasons I can think of to change the name include:
1) The airline has multiple disastrous accidents with much loss of life in a short period of time
2) The airline decides to significantly reposition itself in the market - e.g. becoming much more upmarket
Why else would the company want to spend millions on this and lose the name recognition that all the advertising has bought so far ?