Questions regarding DRMs and rewards after Icebrood Saga

Will DRMs be available after this Saga ends?

Will we get tokens specific to each DRM (and the related faction) or will it become generic ones, regardless of which DRM we complete?

Will all previously possible awards be listed in a vendor inside EoTN at a later date?

The intent of DRMs is replayable content, even after Icebrood Saga is over.

Tyrian Defense seals are the permanent currency you get from DRMs. Faction support marks are obtained and usable only during the time that the faction is at the eye of the north. You can continue to use the faction support marks up until the next faction comes, but you will be unable to earn new faction support marks after the weeklong event is over. Once the faction leaves and there are no more community events, the rewards from that faction will be available for purchase using Tyrian Defense Seals from the permanent vendor.

Yes, the Tyrian Defense Seal vendor houses all the faction rewards after the faction event is over.