Depends on what you're asking. The invitations are not tied to the season. They will continue to be available after the season ends, for as long as it takes for you to complete them all. The final invitation was number nine, and required you to play crucible matches. If you've done that one, you're done (on that character, at least). If you haven't done that one yet, and Xur doesn't have the next one for you, it's most likely due to when you finished your most recent one. Invitations have to be finished by reset on Thursday in order for you to be able to pick up the next one at reset on Friday. If you finished an invitation after reset on Thursday, then you have to wait until Xur comes the following week.