South Africa-born Earle, 29, joined Scarlets from Super Rugby side Cheetahs on a three-year deal in May 2012 and now qualifies to play for Wales on residency.
He moves despite signing a contract extension with Scarlets in March 2015.
Myhill, 24, rose through the Scarlets' ranks playing for Llanelli and Wales Under-20 on the way.
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Blues head coach Danny Wilson coached Myhill in one of his former roles as Scarlets' scrum coach and as a ex-Wales U20 coach.
Wilson said: "Kirby is a talented player of huge potential."
Durban-born Earle has played over 90 games for Scarlets, 13 of them this season after playing for Western Province, Boland Cavaliers, Griquas, and Golden Lions.
Wilson added: "George is a hard-nosed second row forward who is uncompromising and brings real physicality."
Earle came off the bench for Scarlets as they lost to Blues at Parc y Scarlets in the Pro12 at the weekend.
Cardiff Blues have signed Scarlets fly-half Steven Shingler, Hurricanes centre Willis Halaholo, Bristol back Matthew Morgan for the 2016-17 campaign.
Ulster number eight Nick Williams and Saracens' Wales prop Rhys Gill will also join the club from next season.
Scarlets' second row George Earle and hooker Kirby Myhill will join Cardiff Blues at the end of the season.