shaunlub,
It's exciting to hear about your potential use of O365. I'm not a Nintex Employee, but have been using Nintex for years and in a hybrid scenario as well. I'll try to break down a few points you bring up.
A hybrid environments is obviously the the case when you have SharePoint on premise and O365 available for your enterprise. One common practice of hybrid environments is to move content back and forth from one environment to another. Such as moving a published document from on prem to the cloud site. This can be accomplished through workflows and such is available using Nintex. Nintex provides dozens and dozens of actions through its Nintex Live Catalog that you can "install" new actions in your on prem environment to make available for use. Many of these actions are specific to working with sites and documents in o365.
Removing the use of Nintex for minute and focusing on workflows in SharePoint 2013 and O365. It is true that SharePoint 2013 allows for workflows to use one of two workflow services available. These are Windows Workflow Foundation 3 (used also in 2010) and Windows Workflow Foundation 4 (used by the new infrastructure services only available in 2013). A workflow built in 2010 or 2013 using WF3 (2010 method) using SharePoint Designer cannot be upgraded to a SharePoint 2013 (WF4) with the click of any button. I've never had any success with the Export to Visio feature any way. They must be rebuilt. Though 2013 workflows now have a save as template function that is a far improvement.
As of this post, Nintex Workflows built in 2013 on premise do not migrate to O365. Nintex Workflows built in 2013 on premise do still use the WF3 (2010) services. This may change though and Nintex Workflows could soon be available to built on both WF3 and WF4 services.
For workflows handing off responsibilities across the divide, workflows that are on-prem could upload a file to a library on O365 which in turns starts a workflow on that library to perform some further action upon it.
Maybe this doesn't answer all of your questions, but I wanted to get the discussion started.
Best Regards,
Andrew
Thank you very much for the detailed reply. Our worry is, of course, that Microsoft deprecates the SP2010 workflow engine in the next version of SharePoint - with SP2013 workflows, we lost a lot of useful functionality that still remains in SP2010 workflows, and therefore Nintex Workflows (and Nintex makes them a lot easier to build). We always want to be conscious of what is going to happen 2 years or 5 years down the line - to make sure time invested in design now still pays dividends later.
I totally understand, and these are the correct plans to have. From what I gather about SharePoint's design efforts are that they want to obviously continue with WF4 as it is closest to Windows Azure Workflow. It is most likely that if there is another on-premise build of SharePoint that it will still have the Workflow Manager and use a compatible windows workflow service similar to WF4 (if it becomes WF5 it shouldn't be a rebuilt like WF4 was with all new .Net version). But you will still have migration efforts if moving content and processes to a new build on-prem at some level regardless.
A quick note about deprecation. If for some reason a new on-prem build does not have any ability to run 2010 style WF3 workflows, it is possible that you can use your existing farm as a workflow hub. Cross farm workflows can be triggered using Web Services, Rest calls, CSOM, and PowerShell. You could use this ability to provide you with legacy functionality and also extend your migration necessity.
SharePoint 2013 and Windows Workflow Foundation 4 did remove a lot of useful and much needed functionality that WF3 and 2010 had. This was necessary because some steps and impersonations did not fit the new model. But WF4 workflows can start WF3 workflows to allow you to bring in those needed functions.
The most pressing question I think you and I have is when will WF4 workflows through Nintex be available on-prem. I do not know a timeline, but I hope it is soon.