you very rarely ever see an arranger KB on a Pro stage venue at all. Will Musikmesse change the direction this year?

As I have said before, you don't see an arranger on a 'Pro stage venue', because IT IS NOT NEEDED ... For most players, the purpose of an arranger is to augment the sound of an INDIVIDUAL player, so that it sounds like there is more than one person playing ... on MOST 'Pro stage venues' there is a bass player, guitar player, drummer, horns, etc. etc. or any combination of those instruments, which are provided by the arranger ... I often use the sax voice on my arranger, especially when playing bossas ... two weeks ago when I played a gig with my friend Frank playing alto sax, did I use the sax voice on the kb even once? - NO - because he was there to provide that sound ...
A number of years ago I played with a classic rock cover band here in RI ... I used my arranger to provide pianos, strings, some horns etc. depending on the song... I NEVER used the bass, guitar, organ, or drums because there were LIVE players doing that ... in fact, if I had a synth at that time, I probably would have used that instead of the arranger ...
To take it a step further, in many 'Pro stage venues', the keyboard player has several different kbs/synths to use, utilizing the best that each has to offer ...

As for AKBs reverting back to the 'HOME PLAYER', that may be true, because the gigs that arrangers are primarily used for - NH/ Assisted Living/ Senior (55+) communities - are being taken over by people with laptops/iPADs/karaoke machines and a microphone ... OMBs and AKBs replaced small combos, and iPADs and tablets are replacing OMBs ... enjoy what we've got while we can ...