I'm going to elaborate on what Buz said. The Triumph is a Triple--one less cylinder. A triple will have a difficult time revving as high as a 600 I-4. But, in theory, it could have some advantages, too.
Depending on engine tuning, the bigger cylinders could produce a better power from the bottom up, even if it suffers at the the top of the rev range. It's a different engineering solution than the I-4, but it's certainly not a "cheater" like the ZX-6R or the Daytona 650(although I have no problem with the extra displacement in respect to a road bike.)
The 600cc displacement limit is more or less an arbitrary one that became defacto because most of the major manufacturers were making and racing I-4s. And contrary to popular belief, the "Supersport" racing classes are just that--Supersport. Not "600 cc Supersport" or 600cc Inline-four Supersport." To limit the displacement across the board for every type of engine architecture would be unfair to anyone that wanted to try a different engineering solution. And how much fun would that be? The Ducati 749 is a supersport entry. But it needs more displacement (749ccs) to mitigate it's disadvantage in number of cylinders. But the twin layout also has advantages. And isn't that what racing should be about? Who's got the better idea? Jesus, I don't want motorcycle racing to become NASCAR on two wheels.
The company line at Triumph is that they have no plans to go racing. And the WSS or AMA SS rules have not been changed to allow the Triple. But I wouldn't be surprised to see a semi-factory supported team and privateers if the rules are changed and this bike is really good.
Anyway, none of this makes any difference on the road. But to get back to the point, a 600cc I-4 and the 675 Triple is a fair fight.