The Braves could have spent significantly less to "get a proven bat" than the $23 million they spent on Donaldson and his injury concerns - they didn't have to spend it putting someone in Riley's way for the enitrety of 2019. No, that doesn't mean they plan on moving Riley, but they chose to make a "win now" move like bringing Josh in and have followed it up with absolutely nothing other than a downgrade behind the plate and re-signing Markakis - and both of those moves seem more than curious after a go for it signing of a guy like Donaldson.
None of us - myself at the top of that list - has any idea what the plan is, but blocking Riley at 3B for at least another year has to give one slight pause since they've had absolutely no problem with moving Acuna and Albies so fast. As a big Riley believer, I hope the Donaldson/Markakis moves signal nothing other than an opportunity to give Riley another full season to hone his defense and that he'll be the Opening Day 3B in 2020. Camargo and Duvall should get plenty of ABs spelling the two of them, so there should be no need to push Austin to the OF unless they're strictly trying to enhance his versatility OR they feel he may have to move off the position - not leaving the possibility that they're going to move him is just not being realistic about the situation.
Not questioning what you've seen - but I saw a lot of Albies before he was moved off of SS too, and saw little reason to move him until they brought in a better option.