The carriage ride and the speech from the throne can be followed live on NPO1. The broadcast will start at 12:25 GMT+1:
https://www.npostart.nl/live/npo-1
The liveblog of the NPO has a clip about the golden carriage. The German goldsmith explains that gold is cleaned with a mix of water and ... beer. A lady in charge of the restauration of the textile says that it is inevitable that the carriage will be retired to a museum on the long run, as textile is a fleeting material that gets damaged every time the carriage is used.
https://nos.nl/liveblog/2250924-prinsjesdag-oranjefans-in-de-rij-en-drukte-bij-de-kapsalon.html
In 2020 the extensive renovation of the Inner court will start. Apparently the Hall of Knights will also be renovated and the speech will need to be held at another location. The renovation is planned to take 5 1/2 years. I thought the Hall was restored not too long ago, but apparently there is more that needs to be done.
I wonder what other location wil be used. Perhaps one of the churches of The Hague? The gothic hall of Kneuterdijk palace would be ideal, but it must be far too small. I can't think what other places are large & historic enough.