LA JOLLA, CA – Toyota says it will complete its hybrid-electric-vehicle lineup, for now, with the March debut of the new Prius C and Prius plug-in hybrid, but the 4-model stable likely will expand after a couple of years, a top company official predicts.

“With the four cars, you’re seeing the entire Prius family short-term,” Bob Carter, group vice president and general manager-Toyota Div., tells WardsAuto in an interview here. “For the long term, we continue to evaluate it. I certainly have things that I’d love to see evolve.”

Expanding the Prius marque beyond the original model, now dubbed by the auto maker as the “liftback,” was championed by Toyota Motor Sales U.S.A. President Jim Lentz.

Lentz realized the Prius name was sticking in buyers’ minds better than Toyota’s “Hybrid Synergy Drive,” the badging the auto maker bestows on all its hybrid models. So he pushed the parent company in Japan to approve the development of Prius derivatives.

Carter agrees with Lentz: “All I gotta do is say, ‘Prius,’ and people know what it is. Even dyed-in-the-wool, I-don’t-drive-anything-but-a-Ford-Excursion buyers know what a Prius is.”

The first Prius derivative, the family-focused V wagon, went on sale last October. The C, a subcompact, youth-oriented model built on the Yaris platform, arrives in the U.S. next month, as does the PHEV based on the original liftback model.

Toyota executives generally quash talk of putting the Prius badge on light trucks. But Carter is not entirely opposed to doing so, as long as the vehicle isn’t a gas-guzzler.

“‘Prius’ stands for high MPG, efficiency and value,” he says. “So, no, you’re not going to see us put a hybrid in a truck if it doesn’t meet that. I would never support anything with a Prius badge that is sub-40 mpg (5.9 L/100 km). We’re not going to put a hybrid in the Tundra (fullsize-pickup truck) and call it the Prius Tundra.”

Carter beams at the success of the Prius liftback, noting that after 12 years on the U.S. market it still lacks a competitor that matches its 50 mpg (4.7 L/100 km) combined fuel efficiency. From a sales and marketing standpoint, “that’s a huge opportunity for us.”

The expansion of the Prius range appears to be going well, says Carter, touting the early success of the Prius V. The wagon racked up 8,399 deliveries during its first 10 weeks on the market, “more than (the) Chevy Volt (extended-range electric vehicle) sold for the entire year of 2011.”

Two-thirds of the V’s early buyers are making their first hybrid purchase, he says, noting the wagon is helping, not hurting, liftback sales. Buyers are going into Toyota showrooms with the V in mind, but they “decide the original model fits their needs best.”

Toyota is calling for 220,000 Prius deliveries in the U.S. this year, well ahead of 2011’s 136,463. The auto maker blames last year’s relatively meager tally on Japan’s March earthquake and tsunami, which constricted inventory.

Of the projected Prius sales this year, the V and C each are seen comprising 15%-20% of sales, with the plug-in accounting for a 5% share due to its limited rollout. The PHEV’s deliveries will be confined to 14 mostly coastal states with stringent emissions regulations before going national in about a year.

Carter reiterates Toyota’s prediction that the Prius will become the brand’s best-selling model in the U.S., surpassing the Camry sedan by the end of the decade.

Toyota has a goal of having a hybrid derivative of every model in its U.S. lineup by sometime in the 2020s. Carter can’t say how a Yaris hybrid would coexist with the Prius C. “Some of these are down the road, (and) we don’t have them fully planned.”