"I reckon the only way Ianto MIGHT return is if Jack becomes mortal again and he's now able to have a normal relationship without sulking about it."

Oh no-no-no... 'Cause it will cheapen his death scene! Guh...
I just don't get it... like the death of Stephen didn't cheapen it enough. Whose death will Jack be more upset about: his own grandchild or the man we didn't even know if he loved?

And yeah, I totaly agree with tencrush. Even if he's back it all will always be about Jack, and Ianto will be only his love inerest nothing more.