I contacted Michel yesterday and already got a reply:
"Da die enthaltenen Marken frankaturgültig sind, werden sie im Rahmen der MICHEL-Katalogisierung gelistet.
So finden Sie in MICHEL Rundschau 10/2012, Seite 41 die Marken MiNr. 4861 BB - 4864 BB der Ausgabe Baseballspieler vom 20. Juli 2012. Auch weitere Ausgaben werden nach Vorlage in gleicher Weise katalogisiert. Eine Bewertung ist bislang nicht möglich, da noch kein Preisgefüge auf dem philatelistischen Markt erkennbar. Bei Vorlage belastbarer Preisforderungen wird eine Bewertung nachgetragen."
Okay - I guess I'm pretty much the only one here speaking German... :)
What they are saying is that these stamps will and already have been cataloged as these stamps are valid for postage (this is the basic Michel philosophy as any stamp that is valid postage will be cataloged). The Baseball imperf. stamps have been given numbers 4861 BB - 4864 BB and future issues (Michel lags behind a bit) will be cataloged in a similar manner. They also mentioned that - for now - these stamps will be listed without prices as the market for these hasn't really been established yet. That's a fair point for the European market as I haven't seen a single of these newly issued imperf. stamps being sold on
ebay in Germany yet. I also doubt that many overseas collectors are actually aware of these issues.
Time will tell...