From their website:
We're excited to announce, based on your input, we're making a "Return to Power." For the past five years, engine restrictions kept us from offering big-bore engines, which limited our product offerings. Beginning with the 600 hp rollout in January, you'll also start seeing 500hp, 450hp, 380hp and 300 hp models. Watch closely over the next few weeks for more about our "Return to Power."
Part of our 2015 product line will feature The All New Roadmaster chassis. This gives us the ability to offer big-bore Cummins engines and a new world-class independent front suspension system. This is not an "off-the-shelf" standard rail chassis. Our engineers collaborated closely with Freightliner Custom Chassis to offer a redesigned Roadmaster chassis with unique modifications and tuning that gives you the ride and handling you're expecting from our brands.