Text wrapping is not part of SVG1.1, the currently implemented spec. You should rather use HTML via the <foreignObject/>
element.
<svg ...>
<switch>
<foreignObject x="20" y="90" width="150" height="200">
<p xmlns="http://www.w3.org/1999/xhtml">Text goes here</p>
</foreignObject>
<text x="20" y="20">Your SVG viewer cannot display html.</text>
</switch>
</svg>