While I a strong Revan Fanboi, I have to admit sheer probability is with the Empire. While the KOTOR Sith Order may have several fairly competent leaders (Revan, Malak, Karath, etc al.), numerically they are facing an enemy that grossly outnumbers and likely technologically outpaces them. If we assume a 1:1 kill ratio or even a 3:1 kill ratio in favor of the KOTOR Order, the Empire will still win from sheer attrition.
The Star Forge will HELP a lot but unless we see the use of droids on those ships we have little reason to believe the KOTORites will be able to get crews together to take advantage of the SF's power at anywhere near decent levels. In addition, in a straight up fight between Revan or possibly even Malak and Vader the latter is probably going to loose, Sideous cannot be underestimated in any way, shape, form, thickness, width, age, or length. The man IS one of the most- if not THE most- powerful DS users we know of in Canon, and he is a master manipulator.
The only real hope the KOTOR Order has is:
1. They are able to adapt and use Imperial technology and shift it into mass production while keeping their own unique advantages unique (it will not help them if the Empire suddely is able to get access to the old Sith lore that was lost in the interlude between the two).
2. Play a very, VERY careful game of inciting the Empire to rot within by using patsies like say the Canonical rebels as help against the Empire.
3. Above all, KEEPING REVAN IN CHARGE. Revan may or may not be an equal of Sideous, but nobody else in the KOTOR Sith Order is even close. If Malak gets control of the war machine, it is effectively all over for them because Malak's gross lack of strategic and tactical finesse and pathetic PR handling will probably do exactly what it did in KOTOR and rally the people around the Central Government, which makes #2 collapse as people flock to the "enemy you know" and assume that Sideous is the lesser of two evils (no doubt helped by the old bastard's skillful manuevering and propaganda) much like the people of the Soviet Union rallied to Stalin against the Axis whom were if anything even worse than the Red Czar.
4. Strategic planning and tactical luck practically unseen in all of canon.
Since it is highly, HIGHLY unlikely we are unable to get all of those (and even WITH them it would still be very close run) I must give this to the Empire.