The long awaited update is finally here, not version 4 but the beginning to something new that users have been waiting for since the genesis of ProtonMail in 2014.
You can get the update here though the development team, CEO & Co-Founder Andy Yen has received a lot of negative push back, as the update was due to come out last year (2020) not this year.
v4.0 of the desktop application was publicly released last year and included some big UI updates as well as ProtonDrive, ProtonCalendar and ProtonContacts with additional support for ProtonVPN, adding support for the WireGuard Protocol which is open source, faster and more secure than the IKEv2/ OpenVPN protocols.