The pair do not come out of contract until the end of 2015, when their respective two-year deals expire.
Although the club is open to starting talks, the Bombers are comfortable with where it sits for the duo, even if Carlisle and Heppell decide to wait until next year before contract discussions begin, which is considered more likely.
Carlisle is the man of the moment after leading the Bombers to back-to-back wins with a stunning turn of form in attack, while Heppell has put together a career-best season, averaging 28 disposals.
Heppell is a leading contender to claim his first best and fairest award this season, and recently coach Mark Thompson predicted him to be a future captain of the club.
Both just 22, Carlisle and Heppell are important members of Essendon's premiership aspirations, with industry sources believing each would command a salary in the range of $400,000 in 2015 and beyond into their next respective contracts.
The Bombers' list management team has done a strong job in retaining its talent through the expansion era and during its tumultuous ASADA investigation.
Only a handful of senior-listed Essendon players remain unsigned for 2015, although Jason Winderlich has a trigger clause for a second year, and Dustin Fletcher is yet to make up his mind about playing on for a 23rd AFL season.
That decision will be made later in the season in consultation with key personnel.
Talks are ongoing to secure Ben Howlett with a two-year extension, while impressive youngster Marty Gleeson is also out of contract at the end of the season.
Michael Hibberd (three years), Heath Hocking (two years) and Jason Ashby (two years) recently agreed to new deals.
As well as Carlisle and Heppell, next year looms as an important one for the club, with Tom Bellchambers, Jake Melksham, Brent Stanton and Courtenay Dempsey among the vital Essendon players who come out of contract.
