Hi!
The Pro3 seems to be a direct development of the Pro 2. One concern I would have relates to the availability of replacement bearings or the entire Hope line. They are widely available from UK-based stockists, but seem to be difficult to get elsewhere. If you go with the Hopes and plan to travel the world, I would suggest carrying a spare set of bearings with me, or planning ahead for a shipment to arrive from the UK.
For this reason, many world tourists go with simpler Shimano kit, thanks to easy serviceability and widespread availability of replacement parts, perhaps going so far as to carry spare cones or even freehub bodies, according to several accounts I've read. Remember, most custom cassette hubs also use their proprietary freehubs (freewheel mechanism and pawls). If this goes bad, well, it's bad as one will have to await a replacement via FedEx, DHL, or other worldwide carrier at the cost of time and money.
The above comments are in no way intended to slight Hope products, which are of extremely high quality and are renowned for their reliability. It is simply that extended global touring in remote regions brings with it the spectre of parts failures and replacements, and with that in mind, sometimes "simpler" and "available" beats "sophisticated" and "delayed".
Wishing you a safe, wonderful happy trip of a lifetime. Please keep us posted as the time for departure draws near.
All the best,
Dan.