[chernaudi]

The only way that Audi jumping to 4MJ will be a big help is if Toyota stay at 6MJ (which is rumored), and Porsche still have some performance issues with the 919 (not known yet if the 2015 car has fixed all those issues). Also, using the 2014 chassis means no "fasback" rear tub design, so I assume that Audi think that they can make gains elsewhere? Of course, I'd assume that the basic engine/gearbox concept would also carry over, just updated for performance reasons.

But then again, Audi coming out and basically saying that the sprint race package for 2014 was too draggy and the added downforce/drag ate too much into their cars' top speed does seem to suggest that Audi are now willing to sacrifice at least some downforce to get more top speed, provided that it doesn't do too much damage to the older sprint spec's better attributes (helping with tire wear, as well as braking and cornering abilities).

Could Audi just run a high downforce version of the 2014 LM package and/or mix and match parts from the 2014 sprint and LM aero kits?

The fact that Audi did little work on the sprint spec R18s post LM seems to back up the fact that they were working on the 2015 aero package certainly after LM last year, though it would've been neat to see some more of that line of thinking filter in onto the 2014 cars. However, that does suggest that at least some of the 2014 sprint package was a developmental dead end as far as the team was concerned. Also, I'd think that secrecy also played a part, and I do think that Audi are hoping that being a bit ahead of Toyota and Porsche in development might give them an edge at the start of the season.