I'm sure they'll get to it soon, certainly no one's gonna reject a sale - think phil/john/tony have seen the thread and will pass along a reminder to the sales team or a partner where appropriate.
Yes you can upgrade from 6.0.x > 7.1, infact start that process anytime. (Do post exact version/platform being utilized, and as always take a backup.) Then once you purchase you can convert FOSS > NE simply by running the NE installer and applying the license. Version 7 now activates against license.zimbra.com instead of just a local hash check. (Don't forget about
https://buy.zimbra.com for self-serve if under 1k users in a pinch, and they could retroactively apply any necessary discount be-fitting your status. (Though the only truly serious pinches I could think of would entail expired license + 30 days leeway up, but in that case the person hasn't exactly been proactive.)
Keep in mind the sales line to this point hasn't utilized a call-center/direct approach, the numbers go to voicemail and they call you back usually within a day. I'm sure your wait warranted long enough for you to come post here about it - no contest, but if you don't mind might we enquirer the timing between the email (sales@, sales-northamerica@ or contact forum), phone call # 1, and # 2 anyways? (Also remember you're central and their primarily pacific based.) They can obviously look up the details, but it helps when passing along the feedback to know exactly how much time/frustration we're talking about.
Any company could 'shutdown' and not leave behind a way to continue using a particular product, but I'm quite sure VMware (and in turn EMC) is enjoying what Zimbra brings to the table! In such a 'situation' even if the network edition code (MobileSync, MAPI, Backup, HA, etc) weren't released you could still convert back to the completely open source edition - which your customers are already familiar with. If ultra concerned there's a perpetual license option (good for 30-years, the ability to upgrade and fix security discoveries if Zimbra's not around non-withstanding, but at least the clock won't run out).
From another perspective not having enough sales people to take a sheer volume of calls can be a good 'problem' to have! (Support on the other hand is different, I could totally see justification for concern if they didn't return contact within SLA, but the team is pretty good about critical help escalations.)