new feature called "daily workout suggestions" on Edge 1030 Plus will come on future 1030/830/530 firmware too?

This would also be interesting for the Forerunner and Fenix line. I bet Fenix gets it and Forerunner not. 

Will we see this on the edge 830? I assume this is based on Firstbeat algorithm. It would be nice to have.

will this software be made available to existing 1030 or fenix 6 watches

It is not likely that this feature will come to the 530 or 830 as it is licensed from First Beat.  That said, the 1030 did get heat and altitude acclimation after the fact, so it could come, but I would not count on it.

Besides the bigger screen, this really seems like the only significant feature the 1030 plus has over the 830 that has not already be identified as in the works.

If it does not make it to the 830, then it will come to the 830 replacement next year.  From the pattern of things that will likely be an 830plus. 

No, that's this industry all about. You should be able to get 99% of the new features on older devices like Fenix 3 except sensors like spo2 (even if the watch itself cannot support it because older hardware, technically it can be done on the Connect platform). But you don't because they need to push sales. 

The "heat acclimation" is a joke, at least in Louisiana. After a couple rides in the mid-80F degrees it tells me I'm 100% acclimated. Mid 80s isn't even hot!

It uses both temperature and humidity in the calculation. 

Doesn't Garmin own FirstBeat now?