Let's be honest, TG 2018 Black should be invited...They have beaten Capital Blue this year, have also beaten TLC, Hero's, Steps in 2014. Have not beaten Skywalkers Blue or M&D Black though. Also have not played YJ Rose. They are certainly in the top 4 - 8 range of teams.
How would anyone know? Never see them at the top tournaments.
And they did not play STEPS Blue (their A team) in the Fall so maybe beat STEPS White which is the B team.