Audi's Crosslane Coupé concept was revealed in 2012; it's thought to point the way for a compact SUV badged the Q2
The Q4, Audi's planned Evoque rival, is reputed to exist in an advance concept stage
A fuel cell-powered A7 was mooted earlier in 2013; developmental testing was reputed to begin at the end of August
The Audi A3 g-tron runs on compressed natural gas or petrol; it's gas-only range is up to 242 miles
The Audi R8 e-tron is an all-electric supercar. Originally just a concept, it's now due to go into production
Audi's A3 e-tron is a petrol-electric hybrid which is capable of averaging 188.3mpg
A series of recent trademark registrations and applications has provided some insight into Audi's potential future line-up.
While many of the trademarks may simply be in order to protect the company's intellectual property, they appear to correlate with previously mentioned models and concepts.
The most notable is the registration of "SQ2", which would presumably be a high-performance version of the forthcoming compact SUV that could be called the Q2. Audi has previously previewed a concept version of such a car, in the form of the Crosslane Coupé, in 2012.
In a similar vein, "SQ4" - based on the planned rival to the Range Rover Evoque, the Q4 - has been trademarked.
Audi has also seemingly confirmed its plans to expand its SUV line-up further with an application to trademark "Q9", tallying with reports of of a large luxury model that would sit above the current Audi Q7.
The "f-tron" name has also been trademarked, suggesting that Audi may be considering a series production car that utilises fuel cell power.
The manufacturer currently uses the 'tron' moniker on its vehicles that utilise what it claims to be "sustainable technology". Currently, e-tron and g-tron models are offered. These make use of electric, either solely or in hybrid powertrains, and compressed natural gas respectively.
Audi declined to comment regarding the trademark applications and registrations.