Your direct upgrade path would be to upgrade to 7.1TR8,
Then upgrade to Power 8
Then upgrade to 7.2.
7.2 is a real hardware killer, but that's coming from some poor dweeb
that's got a bunch of old crap on his Power 6 (like 0595, 0588, IOP based
Out of 11 lpars of IBM i, spread out over three racks, only two of mine
qualify for 7.2. They happen to be guested lpars which just luckily
happen to have IOPless fiber tape cards. Even those will generate a
message at IPL time something to the effect of "I don't know if you're
using it or not on this lpar but I smell something on this rack that
stinks like HSL/RIO".