Bookmaker William Hill has given a figure of 1/2 that she will top the charts and retailer HMV is expecting huge sales.
The track, recorded at Abbey Road Studios in London with a 77-piece orchestra, displaced Rihanna's Diamonds from the top of the iTunes chart on Friday morning.
The surge of sales is no guarantee of a No. 1 on Sunday and the Official Charts Company said it would be a close-run thing with other popular acts vying for the prized slot.
Managing director Martin Talbot said: "Adele really is helping to put the top hat - or Bond-style black tie - on a classic week for singles.
"Although it will only have two days' sales to contribute towards its Official Singles Chart position this Sunday, Skyfall is likely to be chasing the tails of Rihanna's Diamonds and One Direction's Live While We're Young, both of them brand new singles.
"Given her massive popularity, we wouldn't put it past Adele to add to her many chart records by registering the very first James Bond official No. 1 single, whether this Sunday or in future weeks."
The single's release comes exactly 50 years to the day since the world premiere of the first Bond movie, Dr No. And the film company behind the 007 franchise has designated today Global James Bond Day, with a number of activities to mark the anniversary.
Adele has said she was "hesitant" about recording the song.
But she said: "I fell in love with the script and Paul had some great ideas for the track and it ended up being a bit of a no-brainer to do it in the end.
"I'll be backcombing my hair when I'm 60, telling people I was a Bond girl back in the day, I'm sure."
The film, again starring Daniel Craig as Bond, will premiere on October 26.
Listen to Adele's Bond theme below:
- PA