The former winner of the reality series has been hosting the show since its move to Channel 5 in 2011.
Willis is currently the presenter of spin-off show Big Brother's Bit On The Side, while she also appears on ITV's This Morning.
"Brian has been a great host but Emma is seen by channel chiefs as a true successor to Davina. They're talking to her now about taking over the role from the summer," a source said.
"Like Davina when she hosted the show, Emma's young, a mum of two, and very glamorous. The audience love her on BBBOTS, and execs want to capitalise on that.
"She's thinking it over, but it's a great opportunity and she would be mad to turn it down."
Bosses are said to be considering a swap of shows for the two presenters, but insiders have said that Dowling is unlikely to agree to what would in effect be a downgrade.
Big Brother will return for its 14th series in the summer on Channel 5.