If you're just ripping to m2ts then there'll be no loss in quality as m2ts is the standard container format used on Blu-ray discs.
They usually contain files encoded according to the MPEG-2 Part 2 standard but the Blu-ray specs also support other codecs such as H.264/MPEG-4 AVC or SMTPE VC-1.
Just to add to SJ's remarks, changing container format won't affect quality but re-encoding, transcoding or changing to another codec will.
Re-encoding, transcoding or converting to another codec always decreases quality to some extent however as there's tremendous scope for compression when, for example, converting MPEG-2 to H264 this decrease in quality may not be visually apparent.
In this instance you're not changing anything though so the quality will be the same as the original.