After the two years, if you would like to continue using the built-in data for your mobile data connections, you will need to renew your data plan. This is offered at €43.20 (￡38.40) /year. For the detailed steps on how to do so, please view the following article.
If you wish not to renew, other options include installing your own SIM card or connecting to a Wi-Fi router or a personal hotspot on your phone.
Please note that the renewal of the embedded SIM will only be available for one year after the expiration date. If this one year passes without you renewing the embedded SIM, the SIM will no longer be renewable and you will only be able to use the device by connecting to a Wi-Fi network (tethering to your phone), or by inserting your own third party SIM card into the open nano SIM card slot.