Picture this - for organizations the world over, the only way to survive over the years is to keep ,moving up the value chain. With that analogy, consder relationship is as another amalgamation of processes and deliverables, the fact that marriage is pretty much a stagnant form of set of processes, i think for a happy married life even that marital relationship needs to move up or across the value chain. Adultery, as it is commonly called, will soon be viewed as a means to keep a relationship going by discovering newer value areas, by generations not too far ahead in future. Interestingly, all other relationships allows u the space to move across the value chain, if not then even that relationship goes bad. Eg. if a child stays back home beyond say 22-25 years of his life, he even starts quarrelling with his parents, on the other hand if the child has the space and direction to grow out of the relationship with his parets, he keeps coming back to them all life or even move them in with himself. So the trick is discovering newer avenues.
One might then question the very need to marriage then; valid arguement and perhaps true, which is also wht the future gen will question and increasingly opt out of this age old institution. Choosing to live-in or simply stay "in a relationship" than really convert that to a marriage. And for those who'll convert, will look for value chain progression. This will definitely be a vieled act for few more hundered years, but soon the society will have to open up. So marriage will only be an arrangement where u r sure of who u r coming back home to, with no bindings around who u spend yr day with. Or may be just coz yr kids need a "permanent" set of parents and hence u stay in the marriage. The pressures and distractions of modern life will make a lot of acts hetherto regarded as blasphemy, into a need and convenience for livelihood.
A lot of keepers of the social morality might chose to crusify me for this prediction, but the same happeneded to Newton who first proposed it's the earth that goes round the sun and not the other way round. Doe not chnage a thing about what is true and what is bound to happen.