Mayweather mentions to Ryan that Starfleet has plans to build three more NX class ships in the near future (Enterprise itself, the lead ship of the class, having launched only 4 months ago). We will actually see the next NX class ship, Columbia (NX-02), introduced later in the series; first while still under construction in the season 2 finale, as well as when it was ultimately launched in the season 4 episode "Affliction".