M/s XYZ is engaged in export of goods only having exports of approx. Rs. 5 crores and no clearances for home consumption are affected. M/s XYZ was not required to be registered under Central Excise. Whether M/s XYZ would be required to get itself registered under GST

Yes, because exports have been treated as inter-State supplies under IGST Law.

( FAQ 15: EXPORTS)