Do somebody knows when the Tracker ONE524 will be available?
There isn't a set date for the ONE524. The release will depend on when the existing stock of ONE523 devices is sold out.
Thank you @rickkas7 for the quick response. Would you recommend to start a project with the ONE523 and switch to the ONE524 when it is available?
Is the Cellular coverage the only difference between ONE523 and ONE524?
Will it be possible to sum up both in the same product?
Yes, start with the ONE523. The hardware is identical except for the MFF2 SIM card and you can have both devices in a single product and same firmware.
In many countries in Europe, the EtherSIM (ONE524) and earlier SIM (ONE523) have similar if not identical lists of carriers.