If you go to the Bullet floorplan webpage:
https://www.keystonerv.com/travel-tr...et/floorplans/ at the bottom left of each floorplan diagram that is "new" will be a red "new". At the bottom left of each floorplan that is no longer in production (but available on dealer's lots until all are sold) is a red "stock only". That means the floorplan has been discontinued and can no longer be ordered by a dealer for production.
Keystone does not stock very many trailers at the plant, but rather ships them to dealers as they come off the assembly line, so there is a very slim chance that a dealer can obtain one for you, once the floorplan is no longer in production.
Your choice, the 290BHS doesn't have any annotations that it's being discontinued, so it "should be available" through the remainder of the 2020 production run. Keep in mind that the 2021 models will be introduced in March/April 2020, just 3 or 4 months from now, and the 290BHS may not be in the 2021 lineup. On the other hand, the floorplan may remain in the lineup for the next 10 years... It will depend on popularity, cost to produce, competition from other manufacturers and availability of any special equipment used to produce that model. As an example, if that floorplan is the only one that uses a specific chassis (built by Lippert) and it costs more than anticipated or if Lippert stops producing that specific chassis, then the floorplan might be discontinued. Remember, this is just one example and may not be applicable to the decisions made by Keystone to produce or discontinue that specific model.