I just unboxed my GSF set that I got with christmas cash, and as I was looking through the cards, I came upon the Ancient power source (Back side of the Revenants acherontic archaeology mission). Now, owning Tactics, it struck me as looking extremely similar to the shard depicted on the Oblivion shard scenario power card. And the similarities extend more that just apearace, with the fluff on both refering to the item a source of great power. Since the time frame of Sentinels is long is the past during GSF, anything current in that time frame, it could clearly be ancient by the time GSF occurs if it wasn't already. I really think that they are the same thing.
Another potential link : the Krev na'Void Anachro-Pilot of the Phantom Battleship (from the Syndicate mission "The Phantom", where the Bareg-Threllian recover an ancient "experimental battleship") looks a lot like an Aeon man, from Oblivaeon. Since the Void shards are also featured in the Oblivaeon storyline (and are still - an even bigger ? - part of the storyline in Tactics), those two links could hint towards an even bigger storyline than the Oblivaeon one (one that would span from the SotM timeline to the Tactics one, and into the future depicted in GSF). On hypothesis could be that Oblivaeon himself would reappear in the GSF timeline (he seems to be the one villain fit to the role).