Before I found a touring bike, I used my Giant OCR1 road bike for some commuting. I didn't do an overnight tour, but did commute quite a few times with panniers. I found a Blackburn MTN rack that actually fit my bike and worked quite well. Attaching it at the bottom required a little help from the LBS since there weren't extra braze-ons for the rack alone. It worked, tho.
Definitely try that before buying a new bike.

What kind of touring do you want to try? Overnight by yourself? Fully supported or semi-supported? Just curious, as I love to hear anything about touring.