The New Sith Wars is 2,600+ years after TOR.
Also, the war between the Sith Empire will probably end with the empire shattering after a few decades, but will also probably end up with a shattered republic. What this conflict is leading too is the New Sith Wars and the dark age of the Star Wars universe. What we are seeing is the Roman Empire as the Republic breaking under the weight of corruption and foreign threats.
A fact that supports my point is that when the New Sith Wars start the Republic is a shadow of the one pictured in the Old Republic, while sith space is a dozen clans and small empires owning about 70% of explored space
The one thing this conflict will ensure is the pattern in which the Sith, the Jedi, the Empire and the Republic always rebuilds