The chief target audience of The Best Exotic Marigold Hotel was easy to spot from the blue rinse in their hair. Of course, the same is going to apply with the sequel, so I'm not the slightest bit surprised that Helen Mirren and Colin Firth are "likely" to join up. They make those blue hairs light right up.
Apparently there's also an American actress required to round out the roles in Ol Parker's screenplay - an original, based upon his first film which was, to be frank, also an original, despite ostensibly being based upon the novel by Deborah Moggach.
Roger Friedman at Showbiz 411 nominates Jane Fonda for the American role. I'd prefer Diane Keaton, maybe Swoosie Kurtz.
John Madden will be directing once again, with many of the original cast returning to India. I have a feeling this franchise could run and run. I at least expect a trilogy.