Segway tours around world showcase have been cancelled. There has been no official reason for the cancellations. According the the WDW tours website, the option has now been removed.
However the Wilderness Back Trail Adventure is still available for booking.
Guests who have already booked the Segway around the world, at Epcot, will receive a refund. Guests services are systematically refunding blocks of bookings. This could mean that there is a temporary glitch and they hope to get the Segway Tour back in operation. Until there is an Official answer we are only guessing.