For that to happen the concerned parties should be willing to work together. As it is, Google & Facebook long ended their love relationship...so you can count out G+ and FB integration...And for the rest, they have to feel the need for benefit of "opening up". I doubt there is reason enough for them to work as a collective just for the user's benefit.
In a utopic world where my privacy would be respected and there's no risk of that central search being compromised, I would like it too. But I prefer the exitence of that seperation . My linkedin,twitter,facebook,G+,whatsapp. I like to separate my different worlds. From Whatsapp being the most personal to LinkedIn being more on the professional.