Likely main content and furnishing items only
more interior/exterior housing slots will be added for each type of estate
no exact number communicated yet, but definitely will see an increase
housing slots have increased from 100 (2.0 / Sept 2010) -> 200 (4.x / June 2017) for Small / Cottage, historically speaking
glamour system for housing? (plans exist for 7.x but viability to be determined)
removal of columns (testing, still work in progress)
changing of interior sizes (testing, still work in progress)
Clip: https://www.youtube.com/clip/UgkxnT7kThJZI_n36gJC5no_SITvKyqh-a5k
Source:
Text memo (Japanese) http://blog.livedoor.jp/umadori0726/archives/60881473.html
No huge changes compared to 6.x, but there'll be on-going small updates (AKA no interior / housing on island...)
Yoshi'P and staff joked about they always thought to revisit the submersible system whenever they see comments on it; but no, no plans on making any changes in this area