If you want to see most rides and shows, I'd say you need at least 3 days. I normally do a Disneyland day and DCA day then have a mixed day where I do both parks and clean up what ever rides I did not do or rides I'd like to do more but iif you plan of leaving the parks for hours on end you can easily do 4 days if you want something more of a relaxed style trip
Fantasmic is still down and no date yet
The first two weeks of June Alice, Peter, Toad and Mermaid are down
DCA Rogers show does not start until June 30th
Also no dates on the new Adventureland tree House/Big Hero Six land redo in DCA
Small World still has the Projection show for Encanto if you have not seen that, its a fun little show especially if you watch the firework from there
Knotts is also close and Universal Hollywood as well if you don't want to do Disneyland for more then 3 days.