Yes, if Gandhi were going to send the Prophet to Hun by land, we should see it near Pisa now. The only other thing I can think of is maybe he's going to load him on to a galley (soon to be galleon) near Varanasi. We have a frigate with movement points remaining that could go check it out. Otherwise, if we cant find the Prophet anywhere this turn or next, we should assume he's been settled or bulbed. This assumes entirely logical behavior on the part of the AI; nevertheless, probably the best way to proceed.
If the Great Engineer is still unused next turn, it probably means that Augustus is saving it for Versailles. If that's the case, we might think about researching DR ourselves at some point during the war with India and gifting it to Augustus. We don't want to accept capitulation from Gandhi only to have Versailles built in one of his remaining cities a few turns later. If we follow this scenario, then we need to research DR early in the war, so we have enough time to build Versailles (if Caesar doesn't) before capit from India.
The big question about researching Medicine or not is whether we will get another GM from X-ville. If we don't get a GM from X-ville, researching Medicine doesn't make much sense. If we research toward Medicine now with the intention of building hospitals and RC, and then find out that we don't get a GM from X-ville, there will be no reason to research Refrigeration. How many turns will research toward Medicine take? If we don't go there, can we get victory in sufficiently fewer turns to compensate for the lack of that wonder? Corporation would then be the last tech we need. But building 6 banks (whipped) What about building some of those banks and instead whipping some units as soon as we get CR? and Wall Street (partially cash-rushed) takes at least 5 turns.
So one thing we could try to do is expedite the great person in X-ville. One easy step to take is to give X-ville the fish that Marbleville is using. With the fish, X-ville can hire a 4th merchant and lose only 1 food per turn, getting a GP in 14 turns. If we hired a 5th merchant there, GP comes in 12 turns.
Let's assume we can average an 80% research rate for the remainder of the game. X-ville will lose ~100 beakers per turn when towns are converted to workshops, but other cities coming out of revolt and expanding will add beakers. Let's assume we can average 1300 beakers per turn during the golden age (with the 20% prereq bonus included). If our next techs are Banking-Econ-Constitution-Corporation-Biology, we'll have ~10 turns before we have to decide between Medicine and Refrigeration. That's still 2-4 turns before we know what GP we get in X-ville. This uncertainty is undesirable. Wondering if we shouldn't concede the Medicine-based wonder and concentrate on a faster victory. We could throw in Democracy (3-4 turns) to fill the gap, and find somewhere to start building Statue of Liberty. Or we could just save up some cash so that Biology finishes on the same turn we get X-ville's GP, and then use the extra cash for faster research and cash-rushing.
It's not clear to me what the best course is. We also have to keep in mind the timing of victory. For backdoor diplo, we want to finish the UN 7 turns before we want to trigger victory.