Bioshock is a very much beloved franchise with no technically bad games, it is one of those franchises that you just want to see more stories from as it is ripe with potential. Clearly even Take Two feels the same way about the franchise as the companies CEO Strauss Zelnick has called the series "unquestionably a permanent franchise."
Gamespot picked up the quote during an MKM Partners Investors Conference. Zelnick also went into very minor detail about what the remaining members of Irrational, including co-founder Ken Levine, were up to. He described their small, upcoming project as "something highly creative and innovative."
2016 will mark another three year interval since Bioshock Infinite arrived in 2013, the series past games have all arrived three years after one another so it would not be surprising to hear about a new game very soon. I look forward to where the developers choose to take us next and I am glad to hear that the franchise is a key part of the future.