I revise my thoughts...
They might bring the stadium Boh Rhap stage and show from Australia over to Europe in the summer of 2020, continuing the stadium touring.
If they had Def Leppard, The Darkness and The Struts on the bill they could. With Paul Rodgers they sold out Hyde Park, does Lambert have the same appeal, not for me personally.
They definitely don't need any help from other artists to sell out Wembley (not sure about other UK stadiums). There's always huge demand for Queen + AL in London. What worries me if I'd be able to afford the early entrance/premium tickets. Ticket prices from the USA/ Australia are scary.
But if they played they'd have a full supporting cast. A mini festival like most of their big shows have always been.
Judge for yourself if queen with al could do a bigger audience.
http://m.youtube.com/watch?v=bc-AmpIVJWM
Almost 60.000 they can handle it looks like.
Sure, they didnt come for al
This belongs in the Queen + Adam Lambert section of this forum.