FormerlyHemlock
Hero
Forcecage is also a 7th level spell, and can't be dispelled. I guess I'd argue then that the resilient sphere can block any teleportation magic of less than 4th level, a 4th level spell would require a Charisma save (same mechanic as forsecage vs. teleport) and has no effect on higher level spells. Basically taking the forcecage and extrapolating from it.
To me that seems a bit like extrapolating from 9th level True Polymorph that regular 4th level Polymorph also becomes permanent if you concentrate on it for a full hour: it's an interesting idea and not necessarily something I'd complain about if the DM followed that ruling, but I'd want to be advised of it in advance as a house rule because it's a fairy significant change from the plain reading of the PHB and it would affect my decision-making process. (After all, as a wizard I should know roughly how Misty Step and Otiluke's Resilient Sphere interact, especially if I happen to know them both. It's not like I wouldn't have experimented.)