I find it curious, though, that the Prophecy mentions that "He shall hold a blade of light in his hands ", since Rand has only one hand left. So, maybe "he" is someone else, like Narishma, not Rand?

Of course, even Rand still thinks that he has hands, and he is also shown in one of Egwene's yet unfulfilled Dreams with two hands, so I might be too picky. Probably Rand will channel through Callandor and then the three will become one. I think the three are definitely persons, not cities or countries. "He" might be Rand and "the three" might be his girls. There are after all also other Prophecies which show that Rand and his three girls have to do something crucial together. If Rand's girls really merge than somehow, becoming Ilyena, seems doubtful to me, but remains to be seen.

Otherwise Rand/"he" might be one of the three. In this case the three could be the three ta'veren, or Rand and two female channelers in a circle (Moiraine & Alivia? Elayne & Aviendha? Cadsuane & Nynaeve).

I doubt that Rand, LTT and Moridin are meant, because the end of TGS made pretty clear that LTT isn't distinct from Rand. Besides that, IMO Min's Viewing about Rand merging with another man, one living, one dying, points to Rand's final confrontation with Moridin.