I think not. Not cause they wouldn't love to though, just that they will do it another way.
Rather than make a full fledged FFXV-2/3.... I think they now know (having looked at everyone else) that they cab get away with making really great DLC instead. If they go TLoU or Wither 3 route, they could easily sell 10-15hr worth of DLC for $10-$15 a pop and release as many as 3-6 episodes till at least FF16 is released.
If they are smart, they can support FF15 with DLC for the next 2-3 years and will cost them less to make all round and make them more money over time.







