The deadline is October 15th for the following:

The Wikimania Steering Committee and Wikimedia Foundation are seeking
expressions of interest from interested parties for
 
hosting 
Wikimani
a 2020.
 

Please see the following for more information:

https://meta.wikimedia.org/wiki/Wikimania_2020

If you are interested in discussing the possibilities and working with the
WMF Events Manager in preparing a proposal to host and organize Wikimania
20
20
, please contact eyoung at wikimedia.org by October 15th.  Also, if you
know of an individual or group that we should approach about hosting, we
encourage  nominations as well. The Steering Committee and WMF expect to
make a decision by early 
2019.

Thanks, Ellie