Once again, the problem with making more power in the 1000cc class is that you need to spin the engine with higher rpm than a cvt clutch system can handle. If you want, say, 180 hp without a turbo, you'd probably need at least 14000 rpm. The current apex spins at below 11000 rpm. Sled motors also spin high rpm for longer, and more importantly with a lot more time at full or high load than a sports bike. The current apex has a down-gearing between the motor and the primary clutch to get the primary clutch rpm down to about 8500 rpm max. They could of course down-gear it further for more motor rpm, with higher losses in the down-gearing as a result. I think the biggest problem is getting the reliability for constant high rpm, high load operation to acceptable levels with a higher revving motor.
Edit: Or they could use a turbo or supercharger. I can't imagine they'd ever put a factory turbo on the 4 cylinder motor, because it would be too easy to get too much power out of it, that would upset authorities and insurance companies, plus it would be too easy too fiddle with the boost and break the motor from lack of fuel or over-boost.