Axe-FX III worth getting?
To say something of substance other than "hell yes" I'll say that historically, there have been multiple versions of each Axe-Fx. The 1st had the standard and Ultra versions, then the 2nd Axe-Fx had something like 4 versions. Mark 1, Mark 2, XL, and XL+. The Mark 1 to Mark 2 was a very small update to some parts here and there. The Axe-Fx II to XL was a more significant upgrade as you could store more patches and things like that, more X/Y block functionality, slightly lower noise floor and other odds and ends, but the CPU power was the same, and the original version still had all the same amp models and the same modeling algorithms as the XL+ so from a practical standpoint there wasn't really a whole lot of difference other than that you could have like 700+ patches instead of 500+, which was already more than anybody would ever need. As far as I remember, the XL to XL+ "upgrade" was simply due to Fractal changing the vendors who produced the Axe-Fx's green screen, which necessitated a new product SKU and name. No performance differences.
The Axe-Fx III is still in its Mark I version state, so history indicates that there are still years and years worth of top-of-the-line-ness under the hood in this thing. Personally, I had an Axe-FX II Mark I and never felt any need to upgrade until the III came out.
So to answer your question... "hell yes."