Hybrid trucks aren't likely to show up anytime soon because they weigh and cost too much.
As an example, I'll compare the Honda Accord LX V-6 to the Honda Accord Hybrid. They seem to have similar interior options and power.
The LX weighs 3384 lbs, costs just under $24,000, and gets 21/30 MPG EPA.
The Hybrid weighs 3501 lbs, costs just over $30,000, and gets 39/37 MPG EPA.
So switching to a hybrid drivetrain gives 97% of the payload capacity at 125% of the price for a 186%/123% savings in fuel economy.
Most trucks are going to be operating at highway speeds, so it doesn't look like the hybrid is yet a win for trucking companies. (I don't know if a construction truck would have a load mixture that would allow it to efficiently charge its batteries.)
Kenworth would shave off 5 pounds (or less!) on a part in a new model year to gain fuel economy, since the trucks accumulate over a million miles for their service life. Dropping payload capacity by 3% (1 ton on a truck rated 75,000 lbs) isn't going to be accepted by the market until the fuel savings beat out the extra cost of the hybrid and make up for the payload loss (1 ton of socks is alot of socks!).