Destiny 2 players have been asking to see Forsaken exotics in Xur's inventory for a while now and Bungie are ready to oblige them. Xur will start selling the items starting with the next patch but might not have them on hand immediately.
Xur, Agent of the Nine may think he's a super spook and act like it, but in truth, there is a pile of people who know where he is at all times as his locations are available on Destiny's subreddit. Not only does everyone know his movements, but people can also easily see Xur's inventory for the weekend there.
The thing about his inventory is that players started getting disillusioned with the same old exotics that were available for a long time and wanted Xur's inventory to be refreshed. According to Bungie, this is exactly what's in the update that will happen in the week starting on 04 March 2019.
On the flip side, Xur is not guaranteed to carry one of these exotics immediately as his inventory is on a rotating schedule. This means his exotics pool will still include items from various releases and Forsaken exotics only have a chance to be in his inventory.
Furthermore, Fated Engrams will no longer yield Forsaken exotics but this is something Bungie are looking into and might change in the future. Having more access to Forsaken exotics through the Engrams would be quite enticing and Bungie will likely notify their players ahead of this change.
The same update might change the rolls on armour pieces in order to make Xur's weekly stock "a bit more exciting" which is a welcome change in itself, but another change to Fated Engrams may be even more fruitful for the players.
One fan if Fated Engrams could be changed to roll armour pieces only if the collection is completed, which could further help with getting better rolls. Bungie's community manager responded they would pass the suggestion along to the developers, meaning this change could be on the cards soon as well.