The question about CC 4.0 was just answered in the "Conversation with the Wikimedia Foundation Board of Trustees". This link will take you to the right place:

https://youtu.be/Zpof5J6jjZ4?t=3738

Database rights were mentioned in the answers, along with challenging, unforeseen technical requirements that would require more money, more effort and more technical development work to address than was originally anticipated. As a result, moving to 4.0 is not something the Foundation can commit to doing right now.

The question came up because the UN is apparently close to adopting CC 4.0 for its content.

Andreas

On Thu, Sep 30, 2021 at 9:01 AM Andreas Kolbe <jayen466@gmail.com> wrote:
See also https://meta.wikimedia.org/wiki/Terms_of_use/Creative_Commons_4.0/Diff

The proposed waiver of database rights that was to accompany the move from 3.0 to 4.0 was one of the sticking points, I believe. To quote:

Where you own Sui Generis Database Rights covered by CC BY-SA 4.0, you waive these rights. As an example, this means facts you contribute to the projects may be reused freely without attribution.

For further background see 

https://meta.wikimedia.org/wiki/Terms_of_use/Creative_Commons_4.0/Legal_note#Waiving_database_rights

Andreas

On Thursday, September 30, 2021, Strainu <strainu10@gmail.com> wrote:
Hi Isaac,

See https://meta.m.wikimedia.org/wiki/Terms_of_use/Creative_Commons_4.0

Strainu

Pe joi, 30 septembrie 2021, Isaac Olatunde <reachout2isaac@gmail.com> a scris:
> Hi Strainu,
> I can't find the previous discussions.Could you please provide a link to the public consultations (or proposal) you mentioned to allow people on this list have a clear understanding of what was discussed?
> Best regards
> Isaac
> On Wed, 29 Sep 2021, 23:22 Strainu, <strainu10@gmail.com> wrote:
>>
>> Hi,
>>
>> A few years ago there was a public consultation on moving the Wikimedia license to cc-by-sa-4.0 instead of 3.0. Now, obviously that never happened but I couldn't find the decision documented anywhere. Why was the proposal scrapped? Are there any plans to revisit this?
>>
>> Steainu _______________________________________________
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