Spencer: several new first-party titles in development, but the E3 was for outbound messages
Spencer explained that there are definitely other titles in development, and could have definitely announce a series of games coming up in the next 2-3 years, but the experience of Scalebound -announced too soon and ended up victim of its own hype-instructed us to wait for the announcement of new games only when it is sure that they will cut the finish line in stores.
This means that even for upcoming tradeshows and in the coming years, we should probably expect from Microsoft only listings of upcoming titles, no bombastic revelations of upcoming titles after several years. This also brings with it an advantage for the future: the E3 2018 will probably be full of new ads, since then all games already announced should have already come out, and then we may focus on new titles. This is of course only first-party titles, while according to the agreements made with various publishers will continue to be shown third-party titles even distant in output, as was the case of the beautiful Metro Exodus and ANTHEM .
Spencer has also reiterated that Microsoft is investing heavily on first-party titles, so we should expect several surprises in the coming years.