I don't believe this is the reason. Apparently most of the existing team are going. Some key community members and developers' departures are already confirmed.

http://existdissolve.com/2017/09/a-fond-farewell-to-sencha/ https://mitchellsimoens.com/next-chapter-in-2017/ https://twitter.com/dongryphon/status/911278681611370496 https://twitter.com/AnimalNige/status/911152490380451840 https://twitter.com/evantrimboli/status/910988537763323904 https://twitter.com/elmasse/status/906243331541360640 https://twitter.com/LemmonsGrab/status/911703530716618752 https://www.glassdoor.com/Reviews/Employee-Review-Sencha-RVW...