And given that 3 participants will be booksellers, it seems more than likely that this will be something related to ebooks. When you throw in the media company and and Deutche Telekom it looks like we might be seeing a major new ebook platform. That's what Johannes of lesen.net believes, and I agree that it is a possibility.
I did ask yesterday if the new coalition was buying Nook Media (more as a joke than anything) but did not receive a response. I regard Nook Media as a low probability option, but it's not impossible.
All 3 booksellers have their own ebook/ereader solution, and so does Deutche Telekom. Some of DT subsidiaries telecoms offer an ebookstore built and run by txtr (Hrvatski Telekom in Croatia is one) and DT also has an ebookstore called PagePlace. Also, Deutche Telekom has a history of working with txtr and had planned to sell and support the txtr Reader in 2009, but that device never made it to the market.
Now that I think about it, it's rather curious that txtr wasn't mentioned as being part of the press event. They are not a bit player in the ebook market (certainly not in Europe), so their absence raises interesting questions which will unfortunately have to go unanswered.
I can't wait until Friday.