Chris McNulty - I think this would be a good time revisit some of the comments you left in this discussion: https://techcommunity.microsoft.com/t5/sharepoint/infopath-support-in-sharepoint-online/m-p/97876/highlight/true#M9157
This is definitely an announcement where it will catch a lot of people off guard especially those who are not paying attention to the MS Tech Community. Precedence has been to give more of a longer notice, but with the larger need of cloud services I would guess that 2010 and 2013 Designer workflows are causing a strain on infrastructure which could be better utilized to make services faster. Please consider giving the why's for this decision and timeline?
Also consider publishing an article elaborating on this comment in particular (in the thread linked above):
There is DIFFERENT governance for service removals in Office 365. The strict guidance is that Microsoft will give at least 30 days notice when we've indiciated a replacement product; 365 days notice if there is no replacement; and that undocumented, unsupported features or risks which are found to compromise the security or platform integrity could be turned off immediately. For example, if we found a huge security loophole in the "Widget" web part, for example, we might remove that web part immediately to protect our customers while we work on the issue.
It's scary to think about this as well... I have a hunch that we may even see an announcement regarding InfoPath 2013 EOL soon in SharePoint Online. Our team is scrambling to figure out what we need to license and what we need to do. A 6-9 month timeline would make us feel better about taking these changes on. More time to plan, more time to communicate, more time to implement.