Howto avoid textdata of trace gets truncated?
SSMS always truncates long strings unless typed as XML in which case you can set it to allow unlimited.

The workaround I usually use (from Adam Machanic's workaround to a connect item (internet archive link)) is below
SELECT (SELECT YourTraceDataColumn AS [processing-instruction(x)] FOR XML PATH(''), TYPE)
FROM YourTraceTable

This adds a few leading (&lt;?x) and trailing  (?&gt;) characters but otherwise leaves the data intact and without characters being replaced by XML entities.