Yes, there are three runway options that are part of the consultation launched today. One is the originally-planned 3500m NW runway and the two others have 300m removed from either the eastern or western end (the consultation also makes reference to chopping a bit off both ends, though that's not quantified).
Whatever the length of the runway, it would have a hump in the middle - the thresholds would be at ground level, rising by between 3m and 5m where it passes over the M25.
Lots of other interesting stuff in the (29!) consultation documents, not least the different options proposed for realigning many of the local roads.
https://www.heathrowconsultation.com