If I buy a Stratus will IFLY recognize its output and stabilize the synthetic Vision display on my IFLY presentation?
Yes, but you'll need to use the Appareo Stratus Horizon App to change a setting before this will happen. I think that app is only available to iOS devices. I also think that iFly is trying to figure out how to have iFly change that setting automagically.
By this I mean can IFLY respond to the WiFi from my ADSB and the Stratus at the same time? If mot...why not?
Stratus IS an ADSB-In source with a WiFi output, so, if you are using Stratus as your ADSB-IN source, then yes. However, AFAIK, iFly can only be connected to one WiFi source at a time. If you have another WiFi source in your cockpit you'll have to determine which one you want to use.
I do have the Dynon D10 that serves in IFR, but I would like to see a stable Synthetic Vision from IFLY.
I have the Stratus 3 and use it with iFly both on my 740 and iPad Mini4. I'm VFR only, but the Synthetic Vision seems reasonably stable to me.
As an aside, you might contact Appareo and ask them why they insist on requiring a "i" computer controlled switch to be thrown in order to use the Stratus 3 on non "i" devices. Especially if they don't have a way for non "i" devices to throw that switch. Perhaps they'll consider a software upgrade that allows the output without the necessity of flipping the switch.
As another aside, my 740 DOES connect to the Stratus 3 WiFi regardless of the switch position, but if the switch isn't in the proper position, iFly can't get the Stratus ADSB information despite being connected.