ISU is not on that deal until next year. Forget the exact teams, but I believe 5 or 6 of the 8 teams (Tex, OU not included in the deal) start this year, ISU and 1 or 2 others don't start til 2020/21.
As I understand it, the tier 3 rights change is moving content from individual networks to ESPN+. So, not sure, but I believe each of the 8 teams will have a game on ESPN+ instead of Cyclones.tv, etc. You may be right though.... if ISU is ranked, would ESPN want it on ESPN+ or ESPN/ABC? Not sure if that was spelled out, but I did not see anything about an option for ESPN to move content between the networks (ESPN+, ABC, ESPN, ESPN2, etc.). I think ESPN wants to push viewership / subscriptions for ESPN+, so, wouldn't be surprised if they kept all they can there.... even when a team is ranked.