* New roadmap may run until 2023 - sources
* Say top-level talks may yield decision on 6th model
* Union says expansion must not hurt "Porsche myth"
By Andreas Cremer
BERLIN, Feb 13 Porsche's top managers will soon be drawing up a new expansion plan stretching as far as five years beyond existing targets as the carmaker comes within reach of a 200,000-sales goal, sources familiar with the matter said.
A growing push into sport-utility vehicles (SUVs), spurred by the new Macan model which has sold out eight months of production before hitting German dealerships in April, may push Porsche sales to that level in 2015, three years earlier than targeted, Chief Executive Matthias Mueller said on Tuesday.
Porsche's seven-member management board is pondering a new roadmap that might stretch until 2023, two sources said on Thursday. Porsche's existing "Strategy 2018", drawn up in 2011, also lays out a profit margin of more than 15 percent. Porsche's nine-month margin stood at 18 percent.
A Porsche spokesman said senior management was talking about its longer-term course, but declined to be more specific.
Stuttgart-based LBBW analyst Frank Biller said, "Porsche is aiming to grow profitably. Preserving the brand's exclusivity is key, so any move on investments and products must be gauged very carefully."
Growth and profits at Porsche, bought by VW in 2012, are a major part of efforts to surpass Toyota and General Motors as the world's No. 1 carmaker by volume no later than 2018.
Porsche accounted for more than a fifth of VW group's 8.56 billion euros ($11.63 billion) in nine-months operating profit last year, though it sold only 1.6 percent of group vehicles.
Bolstered by its alliance with Europe's largest carmaker, Porsche sales may rise 15 percent to 233,645 cars and SUVs by 2018, from an estimated 203,171 this year, according to research firm IHS Automotive.
Talks on strategy may yield a decision this year on a possible sixth model line, one source said. Porsche has said a smaller version of its four-door Panamera coupe would be one option to expand its lineup.
A plant near the eastern German city of Leipzig will be expanded further, the source said. Porsche this week celebrated enlargement of the plant after spending 500 million euros on body and paint shops to build at least 50,000 Macans per year.
Booming demand for SUVs may push the share of luxury four-by-fours of overall Porsche sales to 63 percent by 2018 from 47 percent last year, IHS said, thanks to the new Macan which will compete with BMW's X3 model and the Mercedes-Benz GLK.
But the steady push for volume does not thrill everyone at Porsche which advertises itself as a "manufacturer of exclusive premium cars."
"We must ensure that the Porsche myth is preserved," Porsche works council chief Uwe Hueck told Reuters. "Whether this is the case with 200,000 or 250,000 units is something we will have to look at," said Hueck who sits on Porsche's supervisory board, referring to strategy talks with management.
The brand, the product of Porsche's racing heritage and its 911 two-seater, is the main reason for buying a Porsche, Stefan Bratzel, head of the Centre of Automotive Management near Cologne, said.
"Expanding the lineup on the fringes of the pricing range always implies the risk of overexpanding the brand," Bratzel said. "That burdens the image of core products."
Porsche Chief Executive Matthias Mueller, the inventor of the Macan, dismissed concerns that the SUV offensive bears risks for the brand's identity.
Even with Macan sales added, the share of Porsche deliveries of growing passenger-car sales worldwide will stay at about 0.3 percent, according to Mueller.
"The high level of exclusivity of our brand and products will be lastingly ensured," he said. ($1 = 0.7359 euros) (Editing by Louise Ireland)