Lennon signed on loan from Tottenham Hotspur in January, but a deal to sign him permanently is yet to be arranged.
Toffees manager Roberto Martinez told Everton's website earlier this month he felt Lennon had made a 'phenomenal impact', but that talks would only take place at the end of the season.
A deal will come down to whether they and Tottenham can agree a fee, while interest from other clubs could yet complicate matters.
Sako is available on a free transfer after letting his Wolves contract wind down despite their desire to keep him.
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The winger was a key player for Wolves last season, and Premier League interest in his services is of no surprise.
The 27-year-old is expected to stay in England, with the Express & Star reporting that Midlands clubs Aston Villa and West Bromwich Albion are both hoping to sign him.
Lennon is just a year older but has a proven pedigree in England, but is more expensive and it could be considered Sako has more to prove, with his first crack at the Premier League.