Being 25-30 I have yet to see this trend :( and don’t see many of the people I know with partners more than ±4yrs their age.
Moving may solve the problems related to geography, but perhaps not those of culture and lifestyle which often form a larger part of the problem people face. As addressed by others, going to another country may not help any more than simply going to a larger more cosmopolitan city. But even in big cities (London, Paris, New York etc.) it is still possible to be single/lonely, as many are. I think only big changes in lifestyle really solve much of the dilemma such people face.
Lastly, as we get older, we all start to look at people more as future partners even from the outset. This becomes harder as, using nature as an example, it is probably fair to say that the most desirable mates are taken early. Hence those that leave things until later e.g. to focus on career etc., often find things harder and (I dare say) have to settle for less or compromise more. This seems especially true for women who feel their biological clock is ticking and develop the nesting instincts. I suspect this is one of the reasons that in a generally declining/competitive online dating market the sites focused towards marriage in the niches e.g. Jewish/Muslim/Christian matrimonial sites, do well compared to the rest.
Anyway, I am building a dating site to address some of the problems I see and welcome comments/suggestions/ideas of others (your experiences, what you see is broken, solutions). You can contact me at babulmiah{.a.t.]yahoo<,d,o,t,)com. Hopefully, I’ll launch an alpha for HN review soon.