It's likely to be events parallel to the paper Magic plotline. It might well be in the "past", or it could be "current" with a given set - but it will almost certainly not be "current" for long, as paper Magic progresses the timeline much too rapidly.Quote from Evil Never Dies »Quote from Ritokure »That... isn't what a "reboot" means at all. A reboot would imply an all-new continuity. Just like Marvel movies don't "reboot" the Cinematic Universe every time they shift to Ant-Man from Captain Marvel, instead just focusing in a different story in the same universe, this wouldn't be a "reboot" as much as it would be a new story focusing on different characters in the same universe.Quote from Evil Never Dies »
No, not a "separate" storyline as it take place in different worlds but in the same timeline or storyline of the main events, but an all-new storyline which means : A reboot.
Is this going to tell the same story from the card game? No, and that's a good thing. The card game storyline is much bigger than what one could fit into a 20 or even 50 minute episode, and trying to cram in 10+ years of story in such a short timespan always disappoints both old-timers (because the story would lose a lot of the nuance and details that made it interesting in the first place) and newcomers (which would have to "learn" 10+ years of story in a very short timespan). This isn't new, every major expanded universe does this, from the aforementioned Marvel to Star Wars.
They literally said that they will use the same main characters like Jace and Bolas with an all-new storyline. So that means that this series is setted in a near past with totally irrelevants events for the main story until War (so ultraboring and useless spin-off fillers) or, more likely, that they're just going to tell us a completely different story with Jace, Bolas, and so on. Since they just imprisoned Bolas with the premise that was locked forever, you aren't going to say that they just gaves us with such nonchalance the giant spoiler that they will use Bolas again despite we know they can't? Anyway, forgot that this game is actually called "Retcon : the Gathering", if WotC loves to rewrite their own history already in paper magic, you'll see amount of inconsistency fiesta that they'll do here.
The thing you call "useless spin-off fillers" would be very interesting to a lot of people and is one of the more likely candidates. What's happening on Theros, Alara, Ixalan during the timeline of the sets for Amonkhet or Ixalan? The events that we see represented in paper sets aren't the only interesting events on the planes.
I also think you're reading too much into one line. The article says they could use iconic Planeswalkers, and give Bolas as an example. They don't say Bolas will definitely be used; they don't even say that the Russo brothers brought up Bolas - that could just be the author of the article naming a planeswalker he knows. Hell, even if it's accurate and they do mean "use Bolas" and they do mean in the present, that could just mean something like "this powerful artifact was created by Nicol Bolas a hundred years ago before the dragon was sealed away".