I have thought about this too,but I haven't arrived to any plausible conclusion.Doubtless,to be in the only place where he felt happy and felt himself ,but without the person who made it possible,it'd have been a heavy burden for him;heavy enough as not wanting to keep on living a miserable life from that moment onwards,why not?.But on the other hand,his daughter's presence,yes,but also the certainty that he had done what he must do,taking Jack to their first and last home;and,more specially,the certainty that his lover would be waiting for him there,could have given him enough strength to carry on.Sweet memories of the past,sweet hopes for the future... 
Damn, I get emotional so easily nowadays. I'm such a mush inside it's scary. But it's between us

I think Ennis would get the strength to live from his daughters but in the end, I think, it would be a really miserable existence.
Maybe many of you don't agree but memories are what they are, just memories. Their power might not be enough after a longer period of time. Yes, he would have Junior, maybe Jenny - but they would get married one day and leave.
Going to work, getting home ALONE, sleeping ALONE, left with dreams, guilt, always wondering what could have been..
I don't think I'd want to live
About the certainty that his lover would be waiting for him - for me there's no certainty - just the opposite - maybe he will never see Jack again? Never talk to him, never share his moments with him, never see his face.
Knowing all this, knowing what he lost and maybe, will never experience again - Jack, I swear [if I could move back in time I would?]
The question is
Would Ennis be able to forgive himself? For leaving Jack alone?
Losing the chance of the sweet life many people dream of and never have?
Every day, waking up alone, searching the bed for Jack's hand and realizing Jack's not alive anymore?
Just thinking about it makes me suicidal, sorry