Merlin Entertainments Group
2020 - DUPLO Dream Coaster - (12/29/19) According to this post new track for the Duplo Dino-Coaster has begun to arrive at Legoland Windsor. The new coaster will be from Mack Rides and appears to be a clone of the Ba-a-a-Express from Europa Park.
(9/10/19) Legoland Windsor has announced they will add the DUPLO Dream Coaster for the 2020 season, a new kid friendly coaster going in to the DUPLO Valley area of the park, across from the DUPLO Valley Airport attraction. No further details were given as to the make or style of the coaster.
Future Expansion Plans - (5/15/18) Legoland Windsor has been given permission to go ahead with a planned £95 million expansion over the next decade that would add at least three major new attractions to the theme park as well as a resort expansion. The rides in question mentioned a new 13 meter tall indoor ride (likely the and two new outdoot "fairground style" rides. Previously the park had applied to build Ghost: The Haunted House, an indoor walk-through haunt that ends with a family friendly indoor drop / bounce tower ride, but I had heard elsewhere that was no longer the plan.
(6/28/17) Legoland Windsor has submitted a long term development plan for the park that is said to include at least four new rides, a "holiday village", along with improvements to the park entrance and parking areas. New attraction concepts include a whole new themed land for 2019, and indoor ride of some kind of the site previously approved for the Ghost: The Haunted House project that was put on hold and more. More details can be found over at ThemeParks-UK.