We do not have any plans for Active Sync (soon or otherwise).
EWS is an official, documented, supported part of *Microsoft* Exchange since 2007. No reason not to use it, and we're not the only ones who do.
If it's not supported by an "alternative" Exchange server implementation or is buggy (and there are several - incl. Zimbra and Kerio), then that's their problem to fix.
PS - Amazon came out with an "Amazon Work Email" email hosting maybe a year or two ago, also an "alternative" Exchange implementation (i.e. not Microsoft) from what I can tell. They put the effort into making EWS actually work, and Aqua Mail works with it just fine.
No reason why other vendors who develop "Exchange replacement, as good as the real thing" server software couldn't do the same. The documentation is out there.