Yeah, a road bike sounds like it's the best deal for you. If you were going for HIM or IM- I'd say go with the tri bike then ride it regularly the rest of the year. I'm borrowing a tri bike now and I can ride pretty comfy upright (I just don't like to- aero is far more fun). Definitely more comfy in aero, but it's not as bothersome as some friends' tri bikes are in the upright position.
Do you have a bike in mind already?