This of course has no effect on this year's Westercon in Tempe, Arizona, since each Westercon is independently organized.
The full details surrounding this change are moderately complex, and resulted in my adding four new footnotes to the Westercon History List, but if you are not interested in all of that SMOF-filled room stuff, you only need to know that the convention site is now the Hyatt Tech Center and the 2018 Denver Westercon is actually in Denver (barely) rather than one of its suburbs. (Short version of the details: original non-profit group broke up and dissolved; previously announced co-chair left; original hotel not happy with con suites and room parties; lots of rushing around getting things reorganized; some confusion over whether a Westercon has to get someone's permission to "transfer their flag" to another group; new non-profit took over the convention; new hotel found that understands "our" kind of convention.)
Some of you may have seen this announcement on The List That Must Not Be Named, which is nominally closed. I checked with the convention chair while cleaning up the history list and confirmed that this information could be announced in public before posting it to the Westercon web site.