Legendary Metal Gear Solid creator Hideo Kojima has gone on record multiple times saying that he wants to quit the historical franchise, but apparently he isn’t so ready to stop telling the adventures of Snake’s war-torn universe, as he explained in an interview on 4Gamer.
Kojima-san mentioned that the series has always depicted an era in which America was at the top of its strength, but he feels that this idea of a “strong America” is changing. In this sense, he also feels that this (Metal Gear Solid V) is not the end of his own Metal Gear Solid, but the next one may have a different theme.
This is actually quite interesting: Kojima-san could reshuffle the political and military power balance of the franchise. Since Metal Gear Solid 4: Guns of The Patriots is set in 2014, we might very well see a return of the franchise to the present or near future after the dip back in time with Peace Walker and Ground Zeroes/The Phantom Pain. Of course this is just my speculation, but it would be definitely interesting.