FF's battle system has been changing since before KH, so no, it's unrelated.

Nor do I think they're doing a widespread move to ARPG territory. Two games, one of which is a remake (not to mention both starting out as Nomura projects, even if one changed to Tabata), is not a trend. Hell, we have two FF MMORPGs, don't see people worrying that every FF is going to be an MMORPG.

Finally, if KH really had influenced FF like that, the XIII trilogy would be ARPGs, and they're not.