They're not compatible, but not in the way you think.
2012 - 2015 scoots have a notched/bump-cut key, while the 2016 - 2020 models have laser cut keys. The lock cylinders that go into the top-boxes are not cross-compatible (the 2016-20 model being much narrower than the 2012-15).
As a result, if you want to get a newer model bike and transplant your older case, you'll have to keep a separate key for your top box, if it's coming from a older model, and vice versa.
As for racks and mounting equipment, those *ARE* compatible, and you can make the switch, but you can't have unified keying.
In my case, I had a newer top case I got off eBay on a 2014 Sport for a year or so, which transitioned beautifully onto my 2016 when I eventually stepped up.
Hope that helps.