So I contacted ArtaTech and got the following reply:
Hello,
Midia InkPhone “Explorer Edition” is going to be available soon. Please follow our “News” section on https://onyx-boox.com/category/news and Facebook page here: https://www.facebook.com/onyxboox to get the latest information about our products.
E43 will be without problem with IMEI.
Regards,
There is nothing said about a follow-up. But since the current Midia InkPhone is referred to as "Explorer Edition", there is a chance for more editions coming.