As you say you are beginning to train now, so I will assume that you will know sooner than 2 years whether to go or what kind of trip it will need to be to go. On bikes,look for something with a more upright seating position. Touring bikes in general should provide what you need. There are some fast tourers -bikepacking bikes that may be more road oriented for speed over comfort. I would lean toward comfort. I ride a Surly LHT 26" wheeled touring bike as well as a Miyata 610 as touring bikes. The Miyata is slightly sportier and possibly less comfortable for an all-day ride. You need to get to a bike shop and take some for a spin. Think comfort, upright, low gears, wide tires, rack attachment points, durability, easily maintained, as things desirable for a tour.