Here "in comes funky fashionably Portobello Road" means that Portobello Road and Primrose Hill have been added to the Monopoly board game. They have "come in".
"The Strand" was a property on the original Monopoly board - it's a famous street in London. It is not going to appear on the new version of the game so it has "gone out".
Basically, "The Strand", and presumably at least one other place in London which used to appear, have been replaced by Portobello Road and Primrose Hill.