If you look at the overall patch history of Dota2, it's essentially a gradual progress of adding more items and spells, making everything stronger and more powerful, and increasing the complexities, difficulties and skill ceilings of the game to counter stagnation.
Examples are: added backpack, increased max level from 25 to 30, added talent trees, added aghs shards, added neutral items, etc etc.
The past few iterations didn't have many additions besides rotations of neutral items. Eventually the system go stale again and major expansions will be needed.
The next "low-hanging fruit" will be item slots. Note that backpack was added way back in 7.00 (2016).
The last and only Dota2 prediction I made was 3 years ago about the lvl27-30 talent unlock, which had been realized. This 100% record shall continue.
Source: https://www.reddit.com/r/DotA2/comments/xot5sj/prediction_dota2_will_have_8_active_item_slots_by/
